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Brandeis University Law Journal 2023-2024, Volume 11

The Israeli-Hamas War: The Legality of Israel’s Invasion

of Gaza Under International Law

Koby Gottlieb1

The ongoing Israeli-Hamas war continues to cause untold
human suffering, dominate media coverage, and attract the
attention of international organizations. This article seeks to
clarify normative controversy related to the legality of Israel’s
invasion of the Gaza Strip by using international legal norms
regarding self-defense, terrorism, and sovereignty. Using
international legal theory and the expansion of customary law,
as well as the politics between Palestinian factions, the article
finds that Israel’s invasion is legal under current international
law.

I. Roadmap

About three months into the current Israeli-Hamas war,
South Africa brought genocide charges against Israel in the
International Court of Justice (ICJ).2 This article addresses
some of the Israeli arguments made during the court
proceedings, especially those related to self-defense.3 It is

3 State of Israel, Application of the Convention on the Prevention and
Punishment of the Crime of Genocide in the Gaza Strip (South Africa v.
Israel): Verbatim Record, (2023).

2 António Guterres, Secretary-General’s Remarks to the Security Council -
on the Middle East, (2024),
https://www.un.org/sg/en/content/sg/speeches/2024-01-23/secretary-general
s-remarks-the-security-council-the-middle-east; Mat Nashed, Western
Coverage of Israel’s War on Gaza - Bias or Unprofessionalism?, AL

JAZEERA, Oct. 29, 2023,
https://www.aljazeera.com/news/2023/10/29/western-coverage-of-israels-w
ar-on-gaza-bias-or-unprofessionalism; Republic of South Africa,
Application Instituting Proceedings, (2023).

1 Brandeis University, Class of 2026.

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Brandeis University Law Journal 2023-2024, Volume 11

important to first establish the theoretical framework governing
self-defense, terrorism, and territorial sovereignty. This
framework will then be applied to the present case of Israel’s
invasion of the Gaza Strip. After concluding these assessments,
it will become clear that Israel’s invasion on October 27, 2023,
is legal according to international law.

II. Introduction

On October 7, 2023, Hamas carried out a massacre in
Israel, killing about 1,200 people and abducting approximately
240 people.4 In the days following the massacre, Hamas
indiscriminately launched barrages of rockets towards Israel.
Israel consequently launched retaliatory airstrikes. On October
27, Israel began its ground invasion of the Gaza Strip.5 An
in-depth evaluation of the actions on October 7 is not within
the scope of this article; instead, this article evaluates the
legality of Israel’s invasion. Acknowledging the difficulties of
analyzing events during wartime, this article will only address
one question—whether the invasion of the Gaza Strip was legal
under international law—and not the legality surrounding the
events that transpired during the invasion itself. This excludes
any attempt to evaluate Israeli conduct under international legal

5 Israel pummels Gaza with strikes as it expands ground operations, France
24, Oct. 27, 2023,
https://www.france24.com/en/live-news/20231027-israel-pummels-gaza-wit
h-strikes-as-it-expands-ground-operations; ARTHUR VAN COLLER,
Israel-Hamas 2024 Symposium - Qassam Rockets, Weapon Reviews, and
Collective Terror as a Targeting Strategy, (2024),
https://lieber.westpoint.edu/qassam-rockets-weapon-reviews-collective-terro
r-targeting-strategy/.

4 Police say they’ve identified 859 civilian victims from October 7
massacre, up 16, The Times of Israel, Nov. 14, 2023,
https://www.timesofisrael.com/liveblog_entry/police-say-theyve-identified-
859-civilian-victims-from-october-7-massacre-up-16/.

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Brandeis University Law Journal 2023-2024, Volume 11

principles, since any such inquiry would require an in-depth
knowledge of classified information.6

III. The Right of Self-Defense

The United Nations Charter is the foundational text of
the organization, and it is binding upon all member states.7
Article 2(4) of the Charter enshrines the importance of
refraining “from the threat or use of force against the territorial
integrity or political independence of any state.”8 However,
Article 51 of the Charter notes that “nothing in the present
Charter shall impair the inherent right of individual or
collective self-defense if an armed attack occurs against a
Member of the United Nations.”9 Additional codification of
self-defense can be found in United Nations General Assembly
(UNGA) Resolution 3314, which criminalizes state aggression
from the perspective of international law and helps clarify the
definition of an “armed attack” under Article 51 of the
Charter.10 This resolution includes a few examples of acts of
aggression, such as “invasion or attack by the armed forces of a
State… or any military occupation, however temporary.”11 It is
worth noting that the definition of “[s]tate” in this resolution
“is used without prejudice to questions of recognition or to

11 Definition of Aggression, U.N. GAOR (1974).

10 Thomas Bruha, The General Assembly’s Definition of the Act of
Aggression, in The Crime of Aggression: A Commentary, 142 (2016);
Report of the 1956 Special Committee on the Question of Defining
Aggression, (1956).

9 U.N. Charter art. 51.
8 U.N. Charter art. 2, para.4.

7 Alfred Verdross, General International Law and the United Nations
Charter, 30 Royal Institute of International Affairs 342 (1954).

6   NOAM LUBELL, JELENA PEJIC & CLAIRE SIMMONS, Guidelines on
Investigating Violations of International Humanitarian Law: Law, Policy,
and Good Practice, (2019),
https://www.geneva-academy.ch/joomlatools-files/docman-files/Guidelines
%20on%20Investigating%20Violations%20of%20IHL_%20FINAL.pdf.

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whether a state is a member of the United Nations,” meaning
that self-defense against a state can also be legal if the United
Nations does not recognize that state, if that state is not a
member of the United Nations, or even if both are applicable.12

In addition to the Charter and Resolution 3314, the
ICJ’s decision in The Republic of Nicaragua v. United States of
America (1986) is also important in defining self-defense. In
1984, American military intervention in Nicaragua caused the
latter to launch legal proceedings at the ICJ the same year.13

Nicaragua v. USA adds an additional condition for an act of
aggression to justify the right of self-defense: these acts must
be “classified as an armed attack rather than as a mere frontier
incident.”14 The difference between an armed attack and a
frontier incident is based on the “scale and effects” of the
operation.15 The ICJ judgment furthers the importance of
UNGA Resolution 3314 by considering the resolution a
document of customary international law.16 This decision
changed UNGA Resolution 3314 from a non-binding General
Assembly resolution to one that is binding upon all nations, as
is the nature of customary international law.17

The right of self-defense against terror organizations is
more complicated than the right of self-defense against a state;
in fact, it may appear that UNGA Resolution 3314 limits the

17 South West Africa Cases, ICJ 98 (1966); James Crawford, Brownlie’s
Principles of Public International Law 19–28 (9 ed. 2019).

16 Id.
15 Id.

14 Case Concerning Military and Paramilitary Activities in and Against
Nicaragua, ICJ 195 (1986).

13 Carlos Arguello Gomez, Request for the Indication of Provisional
Measures of Protection Submitted by the Government of Nicaragua, (1984),
https://www.icj-cij.org/sites/default/files/case-related/70/9629.pdf; Carlos
Arguello Gomez, Application Instituting Proceedings, (1984),
https://www.icj-cij.org/sites/default/files/case-related/70/9615.pdf.

12 Id.

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right of self-defense to attacks from a state.18 In the interest of
this article, it is imperative to define terrorism under
international law, so that we can evaluate it according to
international legal principles. According to the Special
Tribunal for Lebanon, terrorism has three elements:
“perpetration of a criminal act… or threatening such an act; the
intent to spread fear among the population or directly or
indirectly coerce a national or international authority to take
some action, or to refrain from taking it; when the act involves
a transnational element.”19 As previously noted, UNGA
Resolution 3314 claims that a state must be the body invading
or attacking for it to be considered an act of aggression.

In 2003, the General Assembly requested that the ICJ
investigate “the legal consequences arising from the
construction of the wall being built by Israel” in the West
Bank.20 The opinion of the court became known as The Wall
Advisory Opinion, and while it is only an advisory opinion, it
carries normative weight.21 The Wall Advisory Opinion (2004)
recognized that “Article 51 of the [UN] Charter thus recognizes
the existence of an inherent right of self-defense in the case of
armed attack by one State against another State.”22 Judge
Higgins, former President of the ICJ, offers a dissenting
opinion, concluding that “there is, with respect, nothing in the
text of Article 51 that thus stipulates that self-defense is
available only when an armed attack is made by a state.”23

23 Id. at 33. (separate opinion of Judge Higgins)

22 Legal Consequences of the Construction of a Wall in the Occupied
Palestinian Territory, ICJ 139 (2004).

21 Niccolò Lanzoni, The Authority of ICJ Advisory Opinions as Precedents:
The Mauritius/Maldives Case, THE ITALIAN REVIEW OF INTERNATIONAL AND

COMPARATIVE LAW (2022).

20 General Assembly Resolution ES-10/14, (2003),
https://www.securitycouncilreport.org/atf/cf/%7B65BFCF9B-6D27-4E9C-8
CD3-CF6E4FF96FF9%7D/ICJ%20ARESES1014.pdf.

19 The Prosecutor v. Ayyash et al., 85 (2011).
18 Definition of Aggression, U.N. GAOR (1974).

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Professor Vaughan Lowe, author of numerous books on
international law and professor of international law at the
University of Oxford, strengthens Judge Higgins’ view by
arguing that “the source of [an] attack, whether a state or
non-state actor, is irrelevant to the existence of the right” to
self-defense.24 The opinions of both Judge Higgins and
Professor Lowe carry a level of legal weight because the
International Court of Justice’s Statute recognizes that “judicial
decisions and teachings of the most highly qualified publicists
of the various nations” are means for determining law.25 Based
on their aforementioned qualifications, Judge Higgins and
Professor Lowe demonstrate that they are, as stated by the ICJ,
“highly qualified.”26 Therefore, their opinions are significant
for future evaluation, even though they are not binding.

Raising a further possibility for a right of self-defense,
Nicaragua v. USA states that if a state has “effective control of
the military or paramilitary operations” of a terror organization
while the terrorist organization is conducting acts of
aggression, the state has a level of legal responsibility.27

Moreover, UN Special Rapporteur Philip Alston remarked that
“a targeted killing conducted by one State in the territory of a
second State does not violate the second State’s sovereignty
if… the first, targeting, State has a right under international law
to use force in self-defense under Article 51 of the UN Charter,
because … the second State is unwilling or unable to stop
armed attacks against the first State launched from its
territory.”28 This interpretation allows room for states to fight

28 PHILIIP ALSTON, Report of the Special Rapporteur on Extrajudicial,
Summary or Arbitrary Executions, 35 (2010).

27 Case Concerning Military and Paramilitary Activities in and Against
Nicaragua, 115.

26 Judge Dame Rosalyn Higgins; Vaughan Lowe, QC.
25 Statute of the ICJ, 38(1)d, https://www.icj-cij.org/statute.

24 Vaughan Lowe, Principles of International Law on the Use of Force by
States in Self-Defence, 22 (2005).

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terror organizations in foreign territory without the explicit
permission of the sovereign.

Another advancement in the right of self-defense
relating to terror is represented by UN Security Council
Resolution (UNSCR) 2249. The Security Council passed
Resolution 2249 in November 2015 as a means of combating
the Islamic State throughout the Middle East and the wider
world.29 This resolution “calls upon Member States … to
eradicate the safe haven [the Islamic State of Iraq and Syria
(ISIS)] have established.”30 Importantly, the resolution uses the
language “calls upon,” and these words are “exhortatory rather
than mandatory language and … therefore, they do not purport
to impose any legal duty on any State.” 31 Given the lack of a
legal duty on a state to eradicate ISIS, Marc Weller, Professor
of International Law at the University of Cambridge, argues
that UNSCR 2249 “does not grant any fresh authority for states
seeking to take action,” but rather that this ability has already
existed within international customary law.32 Dapo Akande,
Professor of Public International Law at the University of
Oxford, and Marko Milanovic, Associate Professor in Law at
the University of Nottingham, agree with the assessment that
UNSCR 2249 “neither adds to, nor subtracts from, whatever
authority” states already have in fighting terror.33 The language

33 Dapo Akande & Marko Milanovic, The Constructive Ambiguity of the
Security Council’s ISIS Resolution, Blog of the European Journal of
International Law (Nov. 21, 2015),

32 Arabella Lang, Legal Basis for UK Military Action in Syria, 8 (2015),
https://www.voltairenet.org/IMG/pdf/CBP-7404.pdf.

31 Legal Consequences for States of the Continued Presence of South Africa
in Namibia (South West Africa) Notwithstanding Security Council
Resolution 276, ICJ 114 (1971).

30 Resolution 2249, (2015).

29 Threats to international peace and security caused by terrorist acts,
(2015),
https://documents.un.org/doc/undoc/pro/n15/383/49/pdf/n1538349.pdf?toke
n=S5UY6uLl3akxOfNVQa&fe=true.

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in UNSCR 2249 indicates that the right of states to attack terror
regimes in foreign countries is not new, and that the resolution
simply codified an established rule of customary international
law that has been developing since the Nicaragua vs. USA
ruling.34 The majority of the academic discussion thus far
relates to the right of self-defense against terror organizations
and whether a terror organization is operating in another
sovereign’s territory. Therefore, discussions of what constitutes
sovereign territory and the relevant principles for this
conversation are essential.

IV. Sovereignty, Elements of a State, and Occupation

Article 2(1) of the UN Charter recognizes the idea of
sovereignty of states through the principle of “sovereign
equality” of nations.35 In the Case Concerning the Frontier
Dispute between Burkina Faso and Mali, the ICJ recognized
the principle of uti possidetis juris (as possessing of law) as an
aspect of customary international law. Through this, the court
recognized that the borders of post-colonial states could result
“from mere internal administrative divisions” of the previous
colonial ruler. In this court case, the previous colonial ruler was
France with the former French territories of French Upper
Volta, later Burkina Faso, and French Sudan, later Mali. The
ICJ applied the principle of uti possidetis juris to establish the

35 United Nations Charter, 2(1) (1945),
https://treaties.un.org/doc/publication/ctc/uncharter.pdf.

34 ARABELLA LANG, Legal Basis for UK Military Action in Syria, (2015),
https://www.voltairenet.org/IMG/pdf/CBP-7404.pdf; Michael Scharf, How
the War Against ISIS Changed International Law, (2016).

https://www.ejiltalk.org/the-constructive-ambiguity-of-the-security-councils
-isis-resolution/.

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border between Burkina Faso and Mali based on the French
colonial borders.36

Notably, the case Land and Maritime Boundary
Between Cameroon and Nigeria notes that “the fundamental
principle of respect for frontiers inherited from colonization
[is] uti possidetis juris” and other relevant commitments.37

Other decisions, such as the Land, Island and Maritime
Frontier Dispute between El Salvador and Honduras, have also
recognized the importance of uti possidetis juris.38 Professor
Malcolm Shaw, Professor of International Law at the
University of Leicester, has written that the principle of uti
possidetis juris means that “a new state has the boundaries of
the previous entity.” 39

The Montevideo Convention on the Rights and Duties
of States (1933) is a document of customary international law
that lays out the requirements for a state to be granted
statehood according to international law.40 The Convention
enumerates that for a state to be considered a state under
international law, it must have “(a) a permanent population; (b)
a defined territory; (c) government; and (d) capacity to enter
into relations with other states.”41

41 Montevideo Convention on the Rights and Duties of States, 1 (1933).
40 DJ HARRIS, CASES AND MATERIALS ON INTERNATIONAL LAW (6th ed. 2010).
39 MALCOLM SHAW, INTERNATIONAL LAW 450 (9th ed. 2021).

38 Land, Island and Maritime Frontier Dispute, ICJ (1992),
https://www.icj-cij.org/sites/default/files/case-related/75/075-19920911-JU
D-01-00-EN.pdf.

37 The Land and Maritime Boundary Between Cameroon and Nigeria, ICJ
18d (1998),
https://www.icj-cij.org/sites/default/files/case-related/94/094-19980611-JU
D-01-00-EN.pdf.

36 Case Concerning the Frontier Dispute, ICJ 21–22 (1986),
https://www.icj-cij.org/sites/default/files/case-related/69/069-19861222-JU
D-01-00-EN.pdf.

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V. Palestine and the Montevideo Criteria

There are two paths set out in international law—as
previously explained—that Israel could use to justify its
invasion of Gaza. The first is a determination that it benefits
from a right of self-defense, and the second involves
establishing a connection between previous customary law on
terrorism and Hamas, without relying on the doctrine of
self-defense.

Although both Judge Higgins and Professor Lowe offer
insight into the view that the right of self-defense may come
from a non-state actor, in the interest of a strengthened
argument, the remainder of the article will proceed on the basis
of the majority’s reasoning in the International Court of
Justice’s Wall Advisory Opinion.42 Under that reasoning, the
right of self-defense outlined in Article 51 of the UN Charter
must be self-defense from a state. It is also worth mentioning
that it does not matter whether the state is a member of the
United Nations per UNGA Resolution 3314.43 The determining
factor, therefore, is whether Gaza is a state—which would
include being part of a more comprehensive state—or not.

There is considerable debate among legal scholars on
whether to consider Palestine a state under international law.44

Within the pre-trial proceedings of an International Criminal
Court case to determine whether Palestine is a state, Professor
Malcolm Shaw claimed that “Palestine is not a state according
to international law as it does not conform with the

44 Errol Mendes, Statehood and Palestine for the Purposes of Article 12(3)
of the ICC Statute.

43 Definition of Aggression, U.N. GAOR (1974).

42 Legal Consequences of the Construction of a Wall in the Occupied
Palestinian Territory, at 33 (separate opinion of Judge Higgins); Vaughan
Lowe, Principles of International Law on the Use of Force by States in
Self-Defense, 22 (2005); Legal Consequences of the Construction of a Wall
in the Occupied Palestinian Territory, 139.

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internationally recognized Montevideo criteria.”45 However, in
the same case, the opposition argued for a more lenient
application of the Montevideo criteria in determining whether
Palestine is a state, which could allow it to fulfill the
definition.46 One way or another, however, in determining
whether Palestine is a state that includes Gaza, one must
deploy the Montevideo principles.47

The first point, a permanent population, is easy to
prove—the population of Gaza in 2002 was about 1.1 million
and about 2.1 million in 2023.48 However, it is trickier for a
Palestinian “state” in Gaza to prove it has a defined territory in
accordance with the second criteria. In demonstrating a defined
territory, it must be shown that the “territory is both the object
of the State’s right and the space within which its sovereignty
and jurisdiction are exercised,” as accepted by Professor
Shaw.49 Therefore, it is important to definitely determine the de
facto (based on the reality) and de jure (based on laws) ruler of
Gaza. The borders of the British Mandate on May 14, 1948,
included the Gaza Strip as delineated in an agreement between
the Ottomans and British-ruled Egypt in 1906. This was further
confirmed in a speech in 1925 by the British Minister of State
where he said that “the line dividing the territories under
Egyptian and Turkish administration [was] defined in 1906 by

49 MALCOLM SHAW, TITLE TO TERRITORY IN AFRICA: INTERNATIONAL LEGAL

ISSUES (1986), 15.

48 The West Bank and Gaza: A Population Profile, (2002),
https://www.prb.org/resources/the-west-bank-and-gaza-a-population-profile
/; Gaza Strip, (2024),
https://www.cia.gov/the-world-factbook/countries/gaza-strip/#people-and-s
ociety.

47 Montevideo Convention on the Rights and Duties of States.

46 Office of the Prosecutor, Situation in the State of Palestine,
https://www.icc-cpi.int/sites/default/files/CourtRecords/CR2020_01746.PD
F.

45 Malcolm Shaw, Situation in the State of Palestine,
https://legal-tools.org/doc/p5ixh2/pdf/.

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a boundary commission and has not since been modified.”50

Using the aforementioned principle of uti possidetis juris, the
Gaza Strip de jure belongs to Israel because the Palestinians
only made a declaration of independence in 1988, whereas
Israel did so on May 14, 1948, at the termination of the
Mandate.51

Some may claim that Egypt continued the colonization
of Gaza and therefore, the principle of uti possidetis juris
cannot apply; however, this view is fundamentally wrong. Only
in February 1949, nine months after Israel’s declaration of
independence, did Egypt officially gain control over Gaza
through an armistice agreement.52 But, this armistice agreement
“is not to be construed in any sense as a political or territorial
boundary,” meaning that under the principle of uti possidetis
juris, Egypt’s control of Gaza has no effect on Israel’s
borders.53 Furthermore, in 1979, Egypt and Israel signed a
peace treaty whereby “the permanent boundary between Egypt
and Israel is the recognized international boundary between
Egypt and the former mandated territory of Palestine …
without prejudice to the issue of the status of the Gaza Strip.”54

While this peace treaty recognizes a special status for Gaza,
this does not jeopardize the principle of uti possidetis juris.
Using this principle, Israel could be the only inheritor of the

54 Peace Treaty Between the State of Israel and the Arab Republic of Egypt,
II (1979).

53 Id. at V(2).

52 Armistice Agreement Between Egypt and Israel, (1949),
https://documents.un.org/doc/undoc/gen/nl4/914/45/pdf/nl491445.pdf?toke
n=Oo9YV9LqmAevgIPshD&fe=true.

51 Palestinian National Council Declaration of Independence, (1988),
https://fmep.org/wp/wp-content/uploads/2015/01/PNC-declaration-of-indep
endence.pdf; Declaration of Israel’s Independence, (1948),
https://avalon.law.yale.edu/20th_century/israel.asp.

50 XX REPORTS OF INTERNATIONAL ARBITRAL AWARDS: CASE CONCERNING THE

LOCATION OF BOUNDARY MARKERS IN TABA BETWEEN EGYPT AND ISRAEL, 24–25,
114–116 (1988), https://legal.un.org/riaa/cases/vol_xx/1-118.pdf.

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territory based on the preceding information and the fact that
Israel and Egypt signed the peace treaty nine years before a
Palestinian declaration of independence.55

Others argue that the Israeli withdrawal from Gaza in
2005 indicates a loss of Israel’s de jure status over the Gaza
Strip. However, the Israeli Cabinet Resolution detailing the
withdrawal never mentioned a loss of de jure status and
maintained Israeli operational capabilities within Gaza.56

Therefore, a Palestinian state in Gaza failed on this point—a
defined territory—of the Montevideo Convention.

The third criterion in the Montevideo Convention, the
existence of a government, is also tricky to establish, especially
within Gaza. The challenges arise because the PLO “has been
recognized as the sole legitimate representative of the
Palestinian people” by the Arab League.57 However, since
2006, Hamas has been controlling Gaza, and the PLO,
primarily controlled by the Palestinian Authority, has not been
able to exercise its rule over Gaza.58 A more accurate
presentation would be to label it as controversial whether a

58 Kali Robinson, Who Governs the Palestinians, (2024).; Ian Slesinger, The
Limits of Control: Technological Agency, Urban Terrain, Strategy and the
State in the 2014 Gaza War, POLITICAL GEOGRAPHY (2022); Yezid Sayigh,
Hamas Rule in Gaza: Three Years On, BRANDEIS UNIVERSITY CROWN CENTER

FOR MIDDLE EAST STUDIES (2010).

57 SALEM BARAHMEH, The Palestinians, the PLO, and Political
Representation: The Search for Palestinian Self-Determination, (2014),
https://icsr.info/wp-content/uploads/2014/07/ICSR_Atkin-Series_Salem-Bar
ahmeh.pdf.

56 The Cabinet Resolution Regarding the Disengagement Plan, (2004),
http://www.mfa.gov.il/mfa/foreignpolicy/peace/mfadocuments/pages/revise
d%20disengagement%20plan%206-june-2004.aspx; I acknowledge that
Israel does not claim sovereignty over Gaza, however this does not make
any substantive differences in Israel’s de jure status over the territory.

55 Palestinian National Council Declaration of Independence, (1988),
https://fmep.org/wp/wp-content/uploads/2015/01/PNC-declaration-of-indep
endence.pdf

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Palestinian state in Gaza fulfills the third criterion due to the
lack of a well-established government.

The last point in the Montevideo Criteria is much easier
to prove, irrespective of the controversial status of whether the
PLO or Hamas governs Gaza. The PLO has observer status in
the United Nations and diplomatic representation in about
ninety countries.59 Hamas has definite relations with Qatar and
Turkey and suspected relations with several other countries,
thereby demonstrating its ability to enter into relations with
foreign states.60

While not explicitly a document of customary law, the
European Political Cooperation Declaration on the Recognition
of New States in Eastern Europe and the Soviet Union states
that unless a new state commits itself “to the rule of law … the
Community and its Member States will not recognize” the
state.61 This statement has led individuals such as Tal Becker,
legal advisor for the Israeli Ministry of Foreign Affairs, and
Professor Robbie Sabel, professor of International Law at the
Hebrew University of Jerusalem, to believe that, “even if the
Palestinian entity were to meet those [Montevideo] criteria, the
illegality associated with its current unilateral claim to
statehood demands that recognition be withheld.”62 The

62 Tal Becker, International Recognition of a Unilaterally Declared
Palestinian State: Legal and Policy Dilemmas,
https://www.jcpa.org/art/becker2.htm.; ROBBIE SABEL, INTERNATIONAL LAW

AND THE ARAB-ISRAELI CONFLICT i, 397 (2022); Jeremy Sharon, Israel Rejects

61 Statement by an extraordinary EPC Ministerial Meeting concerning the
“Guidelines on the Recognition of New States in Eastern Europe and in the
Soviet Union,” (1991), http://aei.pitt.edu/36871/1/A2880.pdf.

60 Mirren Gidda, Hamas Still Has Some Friends Left, (2014),
https://time.com/3033681/hamas-gaza-palestine-israel-egypt/; Henri
Barkey, Turkey, the United States, and the Israel-Hamas War, (2023),
https://www.cfr.org/article/turkey-united-states-and-israel-hamas-war.

59 General Assembly resolution 3237, (1974). List of Diplomatic Missions
in Palestine & Palestinian Diplomatic Missions abroad,
https://www.embassy-worldwide.com/country/palestine/.

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illegality that Becker and Sabel refer to is the violations of the
Oslo Accords if the Palestinians establish a Palestinian state
unilaterally.

The Oslo Accords were a series of peace agreements
between Israel and the Palestinian Liberation Organization
(PLO) in the 1990s.63 Professor Watson, former
attorney-advisor in the U.S. Department of State and professor
of international law, regards the Oslo Accords as “binding
international agreements.”64 Unilaterally establishing a
Palestinian state would violate the portion of the Oslo Accords
stipulating that the Palestinian National “Council will not have
powers and responsibilities in the sphere of foreign relations,”
which would be covered by Israel. Thus, unless Israel gives
explicit permission for a Palestinian state, it would be illegal
under the Oslo Accords.65 The Oslo Accords also state that
“neither side shall initiate or take any step that will change the
status of the West Bank and the Gaza Strip.”66 The unilateral
establishment of a Palestinian state would clearly change the
status of the territory that this state occupies. Although the
merits of a Palestinian state fulfilling the Montevideo Criteria
and whether a Palestinian state is legal are unconvincing due to
the aforementioned disagreement on this topic, it is still
important to discuss the legality of Israel’s invasion, assuming
that a Palestinian state exists in Gaza.

66 Israeli-Palestinian Interim Agreement on the West Bank and the Gaza
Strip, Chapter 5 Article XXXI (7) (1995).

65 Israeli-Palestinian Interim Agreement on the West Bank and the Gaza
Strip, Chapter 1 Article IX (5)(a), Chapter 3 Article XVII (4) (1995).

64 GEOFFREY WATSON, THE OSLO ACCORDS: INTERNATIONAL LAW AND THE

ISRAELI-PALESTINIAN PEACE AGREEMENTS (200AD), 101.

63 Oslo Accords, (2024), https://www.britannica.com/topic/Oslo-Accords.

Genocide Claims at The Hague, Says South Africa’s Allegations
“Baseless,” Jan. 12, 2024.

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VI. The Legality of Israel’s Invasion

As previously explained, there are two possible
Palestinian sovereigns of Gaza: Hamas and the PLO. First,
assuming that Hamas is the state sovereign of Gaza, it does not
matter that Hamas does not have representation at the United
Nations nor official recognition as detailed in UNGA
Resolution 3314. One must classify Hamas’ attacks on October
7th as an armed attack. Hamas murdered about 1,200 Israelis
during this invasion, and Hamas forces occupied specific
locations within Israel for at least twenty-four hours.67

Moreover, the attacking forces reached over thirty kilometers
into Israeli territory, reaching Israeli towns as far from the
Gaza border as Ofakim.68 These attacks included about one
thousand Hamas fighters and the combined forces of about five
different Palestinian armed groups.69 Moreover, in the first few
hours of the Hamas invasion, Hamas fired about three thousand
rockets at Israel.70 As defined in the Nicaragua case, this attack

70 Emanuel Fabian, IDF: 9,500 Rockets Fired at Israel since Oct. 7,
Including 3,000 in 1st Hours of Onslaught, Nov. 9, 2023,
https://www.timesofisrael.com/liveblog_entry/idf-9500-rockets-fired-at-isra
el-since-oct-7-including-3000-in-1st-hours-of-onslaught/.

69 DANIEL BYMAN ET AL., Hamas’s October 7 Attack: Visualizing the Data,
(2023),
https://www.csis.org/analysis/hamass-october-7-attack-visualizing-data;
ABDELALI RAGAD ET AL., How Hamas Built a Force to Attack Israel on 7
October, (2023), https://www.bbc.com/news/world-middle-east-67480680.

68 Gil Lewinsky, Bravery in Ofakim: The Civilians, Police Who Thwarted
Hamas Massacre Plan, Nov. 4, 2023,
https://www.jpost.com/arab-israeli-conflict/gaza-news/article-771532.

67 TAMSIN WESTLAKE, An Analysis of the 7th of October 2023 Casualties in
Israel, (2023),
https://aoav.org.uk/2023/an-analysis-of-the-7th-of-october-2023-casualties-i
n-israel-as-a-result-of-the-hamas-attack/; Michael Bachner & Emanuel
Fabian, Israel Evacuates Civilians From Gaza-Area Towns as Forces Scour
for Remaining Gunmen, THE TIMES OF ISRAEL, Oct. 9, 2023,
https://www.timesofisrael.com/israel-evacuates-civilians-from-gaza-area-to
wns-as-forces-scour-for-remaining-gunmen/.

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is not “a mere frontier incident,” but a full-scale invasion, with
ground forces assaulting numerous towns, combined with an
air and rocket attack.71 Therefore, assuming that Gaza is a state
governed by Hamas, Israel would have the right of
self-defense.

The other grounds for an Israeli invocation of the right
of self-defense does not depend on identifying a specific
sovereign of Gaza. Rather, it depends on an analysis of laws
governing state responses to terrorism. The first step is to apply
the definition of terrorism to Hamas. Irrespective of the fact
that over eight countries and the European Union, have
designated Hamas as a terror organization, it is crucial to apply
this definition according to international law as opposed to
domestic law.72 For international law to consider an
organization a terrorist organization, three criteria must be met:

72 El gobierno argentino incluirá al grupo Hamás en la lista de
organizaciones terroristas, FRENTE A CANO, Dec. 23, 2023,
https://frenteacano.com.ar/el-gobierno-argentino-incluira-al-grupo-hamas-e
n-la-lista-de-organizaciones-terroristas/.; Hamas to be listed in entirety as a
terrorist organisation by Australian government, ABC NEWS, Feb. 17, 2022,
https://www.abc.net.au/news/2022-02-17/hamas-palestinian-listed-as-terrori
st-group-australia-government/100839262.; Trudeau affirms support for
Israel in call with war cabinet member Benny Gantz, CITY NEWS, Nov. 16,
2023,
https://toronto.citynews.ca/2023/11/16/no-canadians-on-updated-exit-list-fo
r-the-rafah-border-crossing-hundreds-still-stuck/.; Daniel Boffey, EU Court
Upholds Hamas Terror Listing, THE GUARDIAN, Jul. 26, 2017,
https://www.theguardian.com/world/2017/jul/26/eu-court-upholds-hamas-te
rror-listing.; Paraguay adds Hamas, Hezbollah to terrorism list, MIDDLE

EAST MONITOR, Aug. 20, 2019,
https://www.middleeastmonitor.com/20190820-paraguay-adds-hamas-hezbo
llah-to-terrorism-list/.; Ashlyn Messier, Israel, Australia, Japan, UK, US,
Others Have Officially Designated Hamas a Terrorist Organization, FOX

NEWS, Oct. 13, 2023,
https://www.foxnews.com/world/countries-designate-hamas-terrorist-organi
zation.

71 Case Concerning Military and Paramilitary Activities in and Against
Nicaragua, 195.

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a criminal act, intent to spread fear or coerce a national or
international body to take or refrain from action, and
transnationality.73 International Criminal Court prosecutor
Karim Khan remarked that the cruelties that occurred on
October 7th led him to have “reason to believe” that Hamas’
actions are criminal in nature according to international law.74

Non-state actors are bound by doctrines of customary
international law, including the Geneva Conventions.75

Hamas violated Article III of the 1949 Geneva
Conventions through “murder … mutilation, cruel treatment
and torture; taking of hostages” and more.76 They murdered
over eight hundred civilians on October 7th, raped women, and
kidnapped about 240 civilians and soldiers into Gaza.77 Experts
at the Combating Terrorism Center at West Point have
determined that Hamas’ motivations before, on, and after
October 7th are political, seeking to destroy the State of
Israel.78 Moreover, U.S. President Joe Biden believes that
Hamas intended to disrupt Israeli-Saudi normalization with the

78 Devorah Margolin & Matthew Levitt, The Road to October 7: Hamas’
Long Game, Clarified, 16 CTC SENTINEL (2023).

77 WESTLAKE; Bethan McKernan, Evidence Points to Systematic Use of Rape
and Sexual Violence by Hamas in 7 October Attacks, THE GUARDIAN, Jan.
18, 2024,
https://www.theguardian.com/world/2024/jan/18/evidence-points-to-system
atic-use-of-rape-by-hamas-in-7-october-attacks.; Police say they’ve
identified 859 civilian victims from October 7 massacre, up 16.

76 The Geneva Conventions of 12 August 1949, III.

75 Tatiana Londoño-Camargo, The Scope of Application of International
Humanitarian Law to Non-International Armed Conflicts, VNIVERSITAS 207
(2015).; Legality of the Threat or Use of Nuclear Weapons, ICJ (1996).

74 Yael Freidson, ICC Prosecutor Calls Oct. 7 Hamas Attack on Israelis
“Serious International Crimes,” HAARETZ, Dec. 3, 2023,
https://www.haaretz.com/israel-news/2023-12-03/ty-article/icc-prosecutor-c
alls-oct-7-hamas-attack-on-israelis-serious-international-crimes/0000018c-3
069-da74-afce-b5f926bb0000.

73 Interlocutory Decision on the Applicable Law: Terrorism, Conspiracy,
Homicide, Perpetration, Cumulative Charging, 85.

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said attack, indicating that Hamas had political goals.79 These
points answer the second and third criteria for terrorist
organizations. Using violence for political purposes fulfills the
second criterion; the de facto rulers of Israel and the Gaza Strip
are different, thus making Hamas’ attacks within the de facto
sovereign territory of Israel, a transnational event.80

Given that Hamas is a terrorist organization under
international law, one can use the customary international law
of UNSC Resolution 2249 to prove the legality of Israel’s
invasion.81 Since it is legal under international law for one state
to attack terror organizations outside of their state, one can also
focus on UN Special Rapporteur Philip Alston’s
aforementioned comments on targeted killings in the territory
of another state if that state is “unwilling or unable to stop
armed attacks against the first State launched from its
territory.” 82 While the Israeli invasion is not a targeted killing,
this reasoning may help to establish grounds on which to build
a legal case to prove the legality of Israel’s invasion.83

Benjamin Netanyahu, the Prime Minister of Israel, and other
Israeli defense officials have clearly stated that Israel’s ultimate
goal in launching the invasion is the elimination of Hamas,
which is in line with customary international law.84

84 Chris Brown, After More than 3 Months of Fighting, Even Small Victories
for Israel Are Elusive, CBC, Jan. 20, 2024;
https://www.cbc.ca/news/world/israel-war-goals-unachieved-1.7087509#:~:
text=have%20been%20elusive.-,War%20aims,a%20news%20conference%
20on%20Saturday; Matt Gutman, Israeli Defense Minister Predicts 2 More
Months of War, Then “Mop Up,” ABC NEWS, Dec. 6, 2023,

83 LANG.
82 ALSTON, 35.
81 Resolution 2249.

80 Yezid Sayigh, Hamas Rule in Gaza: Three Years On, BRANDEIS

UNIVERSITY CROWN CENTER FOR MIDDLE EAST STUDIES (2010).

79 Hamas Attack Aimed to Disrupt Saudi-Israel Normalization, Biden Says,
Oct. 20, 2023,
https://www.reuters.com/world/middle-east/hamas-attack-aimed-disrupt-sau
di-israel-normalization-biden-2023-10-20/

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Some may argue that based on the International Court
of Justice Wall Advisory Opinion, Israel does not benefit from
a right of self-defense because Israel does not recognize a
Palestinian state. Hence, the argument may go, the invasion is
not legal.85 However, this ruling is not fully relevant because
the ruling was decided well before the development of the
customary doctrine on dealing with terrorism in 2015, and the
remarks by Special Rapporteur Philip Alston in 2010. This new
evidence demands a fresh understanding of Israel’s rights in
dealing with terror.86

VII. Conclusion

Based on current standing international laws and rules
governing conflict, it is apparent that Israel’s invasion of Gaza
on October 27, 2023 is legal under international law. Since
Gaza is not part of a Palestinian state, Israel does not benefit
from the traditional understanding of self-defense. However,
recent expansions in customary international law, as well as the
opinions of Special Rapporteur Philip Alston, legally
substantiate Israel’s invasion of Gaza, even if Gaza is not a
state in the traditional sense. Although Israel’s invasion may be
legal under international law, this article makes no comment on
the legality of Israel’s conduct during the war. This war has
harmed thousands of Israelis and Palestinians. Moreover, there
is no clear end in sight.87 Hopefully, this article can aid those
seeking to understand the legality of Israel’s invasion by

87 Police say they’ve identified 859 civilian victims from October 7
massacre, up 16; Mounting death tolls in Gaza, war could take months -
WSJ, THE JERUSALEM POST, Dec. 25, 2023,
https://www.jpost.com/israel-hamas-war/article-779421.

86 Resolution 2249, 17.; ALSTON, 35.

85 Legal Consequences of the Construction of a Wall in the Occupied
Palestinian Territory, 139.

https://abcnews.go.com/International/israeli-defense-minister-predicts-2-mo
nths-war-mop/story?id=105377308.

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showing that it is legal under current understandings of
international law regarding self-defense.

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