The UK Parliament is in the midst of a tumultuous debate over whether British forces should participate in airstrikes on Syrian territory. Thus far, the debate has featured frequent calls for Prime Minister David Cameron to apologize for alleged comments regarding the sympathies of those who would oppose Syria strikes. But the international legal basis for British strikes has also arisen, and the meaning of the recent UN Security Council resolution on the Islamic State has been a particular focus. As is so often the case with Council resolutions, the text of Resolution 2249 has given both sides the talking points it needs.
In his speech, Cameron appeared to argue that strikes against IS forces in Syria would be an exercise of direct and collective self-defense (implicitly obviating the need for Council authorization). But he also leaned heavily on helpful aspects of Resolution 2249. For example, he highlighted the Resolution's unanimous adoption and cited its call for states to take "all necessary measures" to restrict IS activities and eradicate its safe haven in Iraq and Syria. Cameron also noted that the resolution identifies the Islamic State as an "unprecedented threat to international peace and security." Listening just to Cameron, one would have the impression that a united Security Council had given outsiders carte blanche to attack IS forces in Syria.
It fell to Labour leader Jeremy Corbyn to point out some of the holes in the Council resolution:
UN Security Council resolution 2249, passed after the Paris atrocities and cited in today’s Government motion, does not give clear and unambiguous authorisation for UK bombing in Syria. To do so, it would have had to be passed under chapter 7 of the UN charter, to which the Security Council could not agree.
Leaving aside the absence of a Chapter VII reference in the resolution, Corbyn might also have pointed out that the key paragraph in the resolution does not provide clear authorization for anything not already permitted under international law. Its urging of states to take all measures necessary—normally Council-speak for new legal authority to use force—is followed immediately by an admonition that measures be "in compliance with international law, in particular with the United Nations Charter..." For all its thunder, Resolution 2249 dodges the question of whether outsiders can use force against IS in Syria without the explicit permission of the Syrian government. As Ashley Deeks pointed out, the language is the result of a careful compromise, mostly betweeen Russia and the West:
Russia is acting against ISIS in Syria with Assad’s consent, and asserts that other bases for using force in Syria are inconsistent with international law. The United States, France, Canada, Australia, Turkey, and other states are using force in Syria on a theory of collective self-defense of Iraq or of national self-defense or both. OP5 neither rejects nor accepts the legitimacy of any particular legal theory. Instead, it indicates approval for states to use force in Syria and Iraq as long as that force is consistent with the UN Charter. That allows states to continue to rely on their existing theories for using force—which each state asserts is consistent with the Charter—without having to resolve the legal dispute between Russia and the other states using force.
Watching the debate unfold, it appears that the British government has got what it needed domestically out of the Council's compromise language. Corbyn's brief intervention aside, Cameron's depiction of the resolution as constituting an authorization to use force has not been directly challenged, and most criticisms of the government's plan for airstrikes have been on non-legal grounds.