The United States, by all indications, will soon become a belligerent in Syria’s civil war. The Syrian government's alleged use of chemical weapons to kill hundreds crossed a redline that U.S. President Barack Obama claimed a year ago would be the game changer, and the game for Washington, London, and Paris has clearly changed. Yet one thing has not: the international law governing when states may use force.
That is not to suggest that government lawyers won’t eventually try to offer some sort of legal benediction. News coverage suggests that administration officials are pushing them to do just that. And the lawyers will want to be helpful, particularly if the policy consensus for force is strong and the evidence for the regime’s responsibility for the attacks is beyond reproach.
But they should also be clear: It is the lawyers’ duty to provide their clients -- senior U.S. officials -- with legal, not moral, advice and counsel. The lawyers’ remit is not to say whether attacking Syria is the right thing to do, but to state what the law is, explain the positions adopted by the United States in similar circumstances in the past, and predict what the legal and institutional consequences of law-breaking might be.
So what is the law? The black-letter law on the use of force is quite simple: Under the United Nations Charter, the central treaty of the modern era and largely the handiwork of the United States and its World War II allies, states are generally prohibited from using force against other states unless they are acting in individual or collective self-defense or pursuant to an authorization of the UN Security Council. Over the post-war history of the charter, self-defense claims have proven most controversial. States -- especially the United States -- have sought to expand the situations that fall under the definition of self-defense.