Oh yeah, the War Powers Act. In 1974, Congress passed, over Nixon’s veto, an act that is supposed to be a guideline of how war powers are split between Congress and the president.
In practice, the president can use troops for 60 days for basically any purpose, but he must made a good-faith effort to inform Congress prior to deploying forces into hostilities, and then those troops may only be kept there for 60 to 90 days without explicit congressional authorization. It also has some reporting requirements so that Congress can be “informed” about what’s going on, but those reports are basically a joke in that they don’t contain much useful information.
http://www.whitehouse.gov/news/releases/2002/09/20020927.html
There’s a sample.
The War Powers Act is viewed by all presidents as a shackle on the commander in chief, and by those concerned with Congressional prerogatives as an inadequate measure of how our country may be sent to war… as long as that war doesn’t last too long. The answer is probably somewhere inbetween – presidents are too power hungry and Congress is too often a micromanager. But as Hamilton said in Federalist 69:
"The President is to be commander-in-chief of the army and navy of the United States. In this respect his authority would be nominally the same with that of the king of Great Britain, but in substance much inferior to it. It would amount to nothing more than the supreme command and direction of the military and naval forces, as first General and admiral of the Confederacy; while that of the British king extends to the DECLARING of war and to the RAISING and REGULATING of fleets and armies, all which, by the Constitution under consideration, would appertain to the legislature. "