The origin of the modern right to self-defense may be traced to the "Caroline Incident" of 1837, which involved a clash between a state (Great Britain) and non-state forces (Canadian rebels and their American supporters). In the aftermath of the sinking of a privately owned ship ("the Caroline") in U.S. territory by British forces, the states involved – the U.S. and Great Britain – agreed that future self-defense operations must meet three cumulative tests: (1) necessity, (2) immediacy (3) proportionality. Necessity and proportionality are recognized as prevailing international law by the ICJ [1], however, the status of the requirement of immediacy in cases not involving preemptive action is unclear.
One initial question raised by the Gaza conflict is whether or not the Hamas rocket attacks on Israel amount to an armed attack, which would accord Israel the right to self-defense. According to the ICJ in the "Nicaragua and Oil Platforms Case" [2], only large scale attacks, and not isolated incidents, justify the right to self- defense (or, in the terms used to refer to the Caroline incident, "render the use of force necessary"). Israel's claim to self-defense appears to meet this threshold since it was based not only on the barrage of rockets fired at Israel after the expiration of the Israel-Hamas ceasefire agreement (on Dec. 19. 2008), but also on the cumulative effect of rocket attacks fired on Israel since 2001, as well as on the gradual expansion of the range of the rockets used by Hamas, which placed approximately one million Israeli citizens within the line of fire.
Still, Israel's self-defense claim is controversial for two main reasons: First, in its advisory opinion cited in the Legal Consequences of the Wall [3], the ICJ ruled that the right to self-defense as it appears under Article 51 of the UN Charter may only be applied against foreign states, and the Palestinian Authority (PA) cannot be considered a foreign state for these purposes. This reasoning would also apply afortiori to Gaza, which is under the control of Hamas.
Second, the ICJ noted in the advisory opinion in the Legal Consequences of the Wall that self-defense claims are precluded in conflicts that take place in occupied territories.[4] Hence, the right to self-defense as recognized by Security Council Resolutions 1368(2001) and 1373(2001) (both are post 9/11 resolutions), has no bearing on the situation in the OPT, which the Court regards as fully under Israeli control. While the Court did not adequately explain this particular point in its opinion, two alternative theorems may be proposed to support the conclusion that it reached: either a self-defense claim under general international law is redundant in circumstances in which the law of occupation authorizes the use of force to restore and maintain law and order (Article 43 of the 1907 Hague Regulations), or a self-defense claim is impermissible if the occupation in itself is deemed equivalent to aggression (which would render any resistance to it legitimate).
Nevertheless, ever since the Israeli disengagement from Gaza and the termination of the IDF's military control over that area in September 2005, as well as the assumption of control by Hamas over Gaza, the situation may have changed. Indeed, Israel's Supreme Court has declared that Gaza is no longer occupied.[5] While this position is not universally accepted, it does seem more plausible than before to argue that the recognition of the right to self-defense in response to terrorist attacks as stated in Security Council Resolutions 1368(2001) and 1373(2001) should also apply to the Israeli-Hamas conflict.
It is interesting to note that during the conflict in Gaza, the Security Council adopted Resolution 1860(2009), which called for the immediate withdrawal of Israeli forces from Gaza. At the same time, the resolution did not mention the role of Hamas in the conflict. Arguably, by ignoring Hamas (in contradistinction to Security Council Resolution 1701(2006), which terminated the Second Lebanon War in 2006 and refers explicitly to Hezbollah), Israel's claim for applying jus ad bellum, as if Hamas had the status of a state, was weakened.
Moreover, the international community was split over the admissibility of Israel's claim to self-defense. On one hand, numerous statements in support of Israel's right to self defense were declared by the UN Secretary General, the former [6] and current U.S. Secretary of State [7] and the Foreign Minister of the Czech Republic (the current EU president). [8] On the other hand, there were those who did not accept Israel's self-defense claim, including the UNHCHR Special Reporter for the OPT, who referred to the existence of diplomatic alternatives as grounds for denying Israel's claim; [9] Bolivia, which described the Israeli claim as "an attempt to rewrite international law based on the doctrine of self-defense"; [10] and the Arab League, which argued that Israel could not claim self-defense because it continues to be an occupying power in Gaza. [11]