And it is that leeway that presidents George W. Bush, Barack Obama and now Trump have used to their advantage. Following the Sept. 11 attacks in 2001, Congress gave Bush authority to attack any countries or groups involved in the attacks, which was generally accepted to mean al-Qaida. Obama used that same authority to fight the Islamic State militant group, which emerged in 2014 as an outgrowth of al-Qaida. Trump has used that same authority to continue military action in Iraq, Afghanistan and Syria. The Obama administration maintained in 2011 that U.S. involvement in the months-long air campaign against Libya didnt require congressional permission because American forces were largely playing a supporting role as part of an international coalition. In February 2015, Obama asked Congress to formally authorize war against the Islamic State, saying the militant group could threaten the U.S. homeland if left unchecked. His resolution would have limited authorization to three years, with no geographic restrictions for U.S. forces. It would have banned enduring offensive combat operations, an ambiguous term that attempted to define a middle ground between Democrats leery of another protracted Middle Eastern conflict involving ground troops, and Republicans, who largely believe the U.S. needs maximum flexibility to pursue IS. Congress held a few hearings, but never acted on the proposal.