On April 6, 2017, 59 Tomahawk cruise missiles launched from U.S. Navy warships struck an air base in Syria. The attack was in retaliation for the horrifying use of chemical weapons, presumably ordered by the Assad regime, against Syrian civilians. Much discussion followed concerning President Trumpʼs authority to launch the strike without Congressional approval, but less attention has been paid to the legitimacy of the missile strike under international law.
Sovereignty is a fundamental principle of international law. States have broad freedom to act as they choose within their own borders and in dealing with their own people, whether or not others like what they do.
The freedom of sovereign states is not absolute, however. There is a balance between the rights of state sovereignty and the stateʼs obligations under customary and treaty- based international law. Of particular relevance to this discussion, the Geneva Protocol of 1925 established the illegality of use of chemical weapons in warfare, and the 1993 Chemical Weapons Convention prohibited production, storage, and transfer of such weapons, as well as their use. Syria is a party to both treaties.
So how is the conflict between state sovereignty and responsibility for the gassing of Syrian men, women, and children to be resolved?
Justifications for the unilateral strike initially offered by the Administration included a strained claim of self-defense (the need to keep chemical weapons out of the hands of terrorists). But Syria has neither attacked nor directly threatened other states. The legal case must rest on a different foundation.
In 2005 the United Nations World Summit adopted the principle of Responsibility to Protect (often referred to as R2P). Under this principle a state has a responsibility to protect its own people from mass killings and other egregious violations of human rights. If the state fails to satisfy that responsibility, intervention by other states can be justified. But under R2P the use of force against an offending state is a last resort (after more pacific efforts). Military action is permitted only in cases of genocide, war crimes, ethnic cleansing, and crimes against humanity, and then only with UN Security Council authorization. Obtaining Security Council authorization for the U.S. missile strike would not have been a practical possibility with Russia and China having veto power in that body. In 2011 the Security Council did authorize (with Russia and China abstaining) military intervention in Libya to prevent atrocities by the Qaddafi regime, but authoritarian regimes consistently resist diminution of sovereignty, and, of course, Russia has a direct interest in supporting the Assad regime.
So R2P cannot be the legal basis of the missile strike in Syria. But that is not the end of the story.
Humanitarian intervention is a concept much older and less institutionalized than the formality of R2P. Under customary international law humanitarian intervention simply involves military force used or threatened against a sovereign state and motivated by humanitarian objectives. Ideally military action justified as humanitarian intervention would be multilateral, as was NATO bombing in the Kosovo conflict in 1999, but that has not always been the case. Because of the conceptual elasticity of humanitarian intervention, and because it challenges the fundamental principle of sovereignty, humanitarian intervention has always been controversial, but it is a recognized part of the framework of international law.
The unconscionable acts perpetrated against the Syrian people for years by the Assad government, culminating in this most recent outrage of chemical attacks, manifestly justify the missile strike of April 6. The legal case based on humanitarian intervention is sound, if not universally embraced. It is virtually impossible to contest the moral case.
Robert Thompson is a retired lawyer and international business executive. He currently is president of the Tucson Committee on Foreign Relations.