by Samantha Arrington Sliney – Shortly after the beginning of the Syrian Civil War, the Islamic terror group ISIS captured the world’s attention with their rapid advance through Iraq and acts of severe brutality. In short order, the group captured large swaths of territory in Iraq and Syria and declared the formation of an Islamic State. With the integrity of Iraq in the balance, the United States committed to taking military action against ISIS but quickly discovered that as pressure was put on ISIS in Iraq they retreated into Syrian lands, where U.S. warplanes could not go.
This article explores the legal justifications for the use of military force that the United States may invoke to take military action against ISIS in Syria. Beginning first with a history of the Islamic State in Iraq and Syria as an outgrowth of al-Qaeda and tracing its actions through the Middle East, the article finds three justifications for using force in Syria to halt the advance of ISIS. Under customary international law the article finds a possible avenue under the long-standing principles of express and implied consent. Second, the article explores the consequences of proceeding under United Nations Security Council authorization, absent the consent of Bashar al-Assad. Finally, the article explores the intricacies of proceeding under various notions of self-defense under Article 51 of the United Nations Charter.