On August 8, 2014 the US began airstrikes against the Islamic State in Iraq. The US has since expanded its operations into neighboring Syria. President Obama and his administration proceeded with the airstrike campaign without official congressional approval. Debate surrounding the legality of the US actions began almost immediately.

Article 1 of the US Constitution vests traditional war powers to congress, including the powers to declare war and authorize military use in hostilities. However, in 1973, congress passed the War Powers Act, which grants the president limited power to authorize use of military in times of need. The act stipulates reporting requirements and limits any engagement to 60 days absent congressional authorization. President Obama cited this authority under the War Powers Act in an initial letter to congress for airstrikes targeting IS, dated August 8, 2014. In late September 2014, the president expanded this, citing both his power under the War Powers Act and the 2001 Authorization for Use of Military Force (AUMF). Congress passed the AUMF following the September 11, 2001, terrorist attacks in an effort to give President George W. Bush unilateral power to use force against any nations, groups or persons deemed to have planned, carried out or aided in those attacks. The AUMF has since been used to support attacks against the Taliban, Al Qaeda and other terrorist organizations associated with September 11, 2001.

In a press conference, US Press Secretary Josh Earnest and US Deputy of National Security Ben Rhodes claimed IS is included under the law given its origination from a sect of Al Qaeda in Iraq. Controversy surrounds this invocation of the AUMF and some, including US Senator Rand Paul, argue that there is no ground to use this law as justification for action against IS. Critics of the Obama administration’s decision also point out that the president is using the same law that his administration urged congress to repeal in July 2014. The Obama administration’s approval of airstrikes caused similar debates in 2011 when the administration invoked its “constitutional to conduct foreign relations” under the War Powers Act to justify similar air strikes and aid to Libya.

President Obama has also defended airstrikes against IS under international law. At the UN Security Council in September 2014, Obama argued that the strikes were legal under Article 51 of the UN Charter. In cooperation with the Iraqi government and with the support of other nations, the US department holds that these actions are in line with a nation’s right to participate in collective self-defense against the acts of IS.