Controversy continues over the appropriate role that Congress should play in regulating U.S. military operations against foreign entities. U.S. action against Libya reignited consideration of long-standing questions concerning the President's constitutional authority to use military force without congressional authorisation, as well as congressional authority to regulate or limit the use of such force. As Congress considers defence authorisation and appropriate bills, there may be renewed focus on whether or to what extent Congress has the constitutional authority to legislate limits on the President's authority to conduct military operations in Afghanistan, Iraq, Libya, or other locations. This book discusses the constitutional provisions allocating war powers between Congress and the President, and presents a historical overview of relevant court cases, and other considerations which may inform congressional decisions on war powers.