Ongoing U.S. military operations against the Islamic State (which formerly referred to itself as the Islamic State of Iraq and the Levant, and is also commonly referred to as IS, ISIS, or ISIL) raise issues concerning the allocation of war powers between Congress and the President, including whether such operations have been (or are required to be) authorized by an act of Congress. In August 2014, President Obama ordered U.S. forces to commence airstrikes against IS targets in Iraq to assist the Iraqi government in combating the insurgent force, protect U.S. military and nonmilitary personnel in Iraq, and support certain humanitarian operations. In a public address on September 10, 2014, President Obama announced the pursuit of a strategy to "degrade and ultimately destroy" the Islamic State, including through the escalation of U.S. airstrikes against IS forces in Iraq, as well as the possible initiation of U.S. airstrikes against IS forces located in neighboring Syria. On September 23, 2014, the United States began airstrikes in Syria targeting IS forces and certain other groups within that country believed to be affiliated with Al Qaeda.As of the date of this report, Congress has not enacted legislation specifically authorizing U.S. force against the Islamic State. In enacting the Continuing Appropriations Resolution, 2015 (P.L. 113-164), which was signed into law on September 19, 2014, Congress authorized the President to arm and train vetted elements of Syrian opposition groups, including for purposes of deterring attacks on the Syrian populace by the Islamic State, but the legislation expressly provides that it does not constitute statutory authorization for the introduction of U.S. forces into actual or imminent hostilities. Initially, the Obama Administration cited the President's authority under Article II of the Constitution as the legal basis for U.S. operations against the Islamic State. More recently, however, the Administration has claimed that the 2002 Authorization for Use of Military Force Against Iraq (2002 Iraq AUMF; P.L. 107-243) and the 2001 Authorization for Use of Military Force (2001 AUMF; P.L. 107-40), provide congressional authority for military operations against the Islamic State. Some observers and Members of Congress have expressed disagreement with this interpretation, though it is unclear whether any dispute over application of these statutes to the Islamic State would give rise to a cognizable claim that would be resolved by the courts.This report addresses select legal questions raised by the use of military force against the Islamic State. Questions addressed in this report include potential sources (and limitations) of presidential authority to use military force against the Islamic State without express congressional authorization; the potential relevance of the 2002 Iraq AUMF, the 2001 AUMF, and the Continuing Appropriations Resolution, 2015; the constraints imposed by the War Powers Resolution upon U.S. military action that has not been authorized by Congress; and the applicability of the United Nations Charter to ongoing U.S. military strikes in Iraq and Syria. The report will be updated as warranted by events.