The hundreds of U.S. troops who are still stationed in Syria, on a mission to “maintain the enduring defeat” of the Islamic State (also known as ISIS), are fighting an off-and-on battle with Iranian-backed militias. Just last week, the United States conducted strikes against fighters described as “Iran-supported malign actors” who attacked a base housing U.S. troops in eastern Syria. It is not the first time this has happened. Since 2016, U.S. forces in Syria have fought not only members of ISIS but also Syrian government troops, Iranian-backed militias, and Russian mercenaries. This longer list of adversaries shows what a complex and perilous environment U.S. forces are operating in and raises questions about the underlying legal rationales for their deployment.
Both domestic and international laws restrict war making, and thus, in principle, the president is restrained from unilaterally using military force whenever he or she desires. U.S. law makes exceptions for cases of self-defense and conflicts that are approved by Congress, and international law similarly allows for self-defense and force approved by the UN Security Council. But with both Congress and the UN Security Council reluctant to approve conflicts for both policy and political reasons, the U.S. government has figured out creative ways to circumvent these bodies. Nowhere is that clearer than in Syria, where successive U.S. administrations have engaged in clever legal maneuvering to fit a wide range of U.S. operations within the scope of domestic laws. The original rationale for going to war in Syria in 2014 was to fight ISIS and al Qaeda. Although Congress did not authorize the campaign against ISIS in advance, it subsequently appropriated funding for U.S. counter-ISIS operations. Yet since 2016, U.S. forces in Syria have also battled a handful of other foes with no congressional authorization or even debate.
