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. On September 10, 2014, President Obama announced the pursuit of a strategy to "degrade and ultimately destroy" the Islamic State, including through 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. The capture of significant portions of Iraqi territory in June 2014 by the Islamic State prompted significant military operations by U.S. forces in Iraq for the first time in more than three years. Between March 2003 and the end of 2011, the U.S. military forces had been deployed in Iraq first to remove the Saddam Hussein regime from power and then to assist the nascent post-Saddam government in responding to threats to the country's stability. Following the expiration of the U.S.-Iraq Security Agreement at the end of 2011, offensive U.S. military operations in Iraq were terminated and most U.S. forces were withdrawn from the country. In the wake of the successful offensive in northern and central Iraq by IS forces in June 2014, however, the Iraqi government requested U.S. assistance in responding to advancing IS forces, including through airstrikes. Shortly thereafter, the United States deployed military personnel to collect intelligence and logistical information regarding IS activities, advise Iraqi security forces, and bolster protection for U.S. personnel and facilities within Iraq. In early August, President Obama authorized U.S. forces to begin limited airstrikes against IS forces to stop further advances and to protect U.S. military and nonmilitary personnel, including those providing humanitarian assistance to Iraqi civilians trapped by IS-led forces on the Sinjar Mountain. A week later, President Obama authorized additional airstrikes to assist Iraqi forces in recapturing the Mosul Dam from IS forces. U.S. airstrikes were subsequently authorized in support of an operation to deliver humanitarian assistance to civilians located in the town of Amirli and to prevent an IS offensive against the Haditha Dam in Anbar Province. Continuing activities by the Islamic State, including the group's apparent responsibility for the execution of two U.S. journalists, led some policy makers to consider the possibility of expanding the scope of U.S. military action against the group, including potentially targeting IS forces located in Syria. 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 of 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 the Khorasan Group, which is believed to be an element of Al Qaeda. 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 ) confer congressional authorization 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. As of the date of this report, Congress has not enacted legislation specifically authorizing U.S. force against the Islamic State. As part of the Continuing Appropriations Resolution, 2015 (2015 CR, 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. Legislative proposals have been introduced, including H.Con.Res. 105 , passed by the House in July, and provisions within the House-passed version of the Department of Defense Appropriations Act, 2015 ( H.R. 4870 ), which appear intended to constrain the executive's ability to engage in certain types of military action in Iraq or Syria without congressional authorization. Other legislative proposals have been introduced that would expressly authorize the use of military force against the Islamic State, though in some instances these authorizations would limit the ability to deploy ground troops into combat operations, or would authorize force only for a limited period. 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 assuming the absence of express congressional authorization; the potential relevance of the 2002 Iraq AUMF, the 2001 AUMF, and the Continuing Appropriations Resolution, 2015 (2015 CR, P.L. 113-164 ); 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. Many of the legal issues discussed in this report concerning congressional oversight of U.S. military action are addressed in greater detail in CRS Report R41989, Congressional Authority to Limit Military Operations , by [author name scrubbed], [author name scrubbed], and [author name scrubbed]. Further discussion regarding U.S. operations against the Islamic State in Iraq and Syria can be found in CRS Report R43612, The "Islamic State" Crisis and U.S. Policy , by [author name scrubbed] et al. ; Iraq Crisis and U.S. Policy , by [author name scrubbed] et al. ; and CRS Report RL33487, Armed Conflict in Syria: Overview and U.S. Response , coordinated by [author name scrubbed]. Until recently, the executive branch cited only to the President's independent authority under Article II of the U.S. Constitution as the legal basis for the military action taken against the Islamic State. Some observers and lawmakers questioned whether some or all of these actions are lawful without congressional authorization, and some wonder whether or at what point further military action would require express congressional approval. While the Executive has recently claimed that the 2001 AUMF and 2002 Iraq AUMF provide statutory authorization for military action against the Islamic State, questions remain as to whether the President possesses independent authority to order the use of force against the group even if these statutes are deemed to be inapplicable or are subsequently repealed or narrowed by legislation. The Constitution divides authority between Congress and the President on matters of war and the use of military force. Under Article I, Section 8, Congress has the power to declare war, tax and spend for the common defense, provide for the army and navy, make rules regulating the Armed Forces, and make rules concerning captures. Additionally, Congress has authority to make all laws "necessary and proper" for carrying out not only its own powers under Article I, Section 8 but also all of the powers vested by the Constitution in the executive and judicial branches as well. On the executive side, the Constitution vests the President with the "executive Power," and appoints him "Commander in Chief of the Army and Navy of the United States," and bound to "take Care that the Laws be faithfully executed." He is also required by oath to "faithfully execute the Office of President of the United States," and, to the best of his "Ability, preserve, protect and defend the Constitution of the United States." Although not explicitly made plain by the Constitution, he is also understood to be primarily responsible for carrying out the country's foreign affairs. The circumstances when the executive may order the use of force without congressional authorization have been the subject of long-standing inter-branch and scholarly debate. The executive has long asserted that the President has independent authority to conduct at least some military operations in the absence of an authorizing act of Congress, including protecting U.S. persons abroad (and possibly foreign nationals, as well), repelling attacks against the United States or its military forces, or defending a "national interest" of the United States. In legislative enactments, however, Congress has characterized the President's independent constitutional authority to introduce U.S. forces into hostilities as being significantly more limited in scope. Notably, the War Powers Resolution of 1973 declares Congress's view that The constitutional powers of the President as Commander-in-Chief to introduce United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances, are exercised only pursuant to (1) a declaration of war, (2) specific statutory authorization, or (3) a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.