Congress wrote that authority into law in the National Defense Authorization Act two years ago, prompting outrage from civil libertarians on the left and right. President Barack Obama signed the measure, but insisted his administration would never use it.

Supporters of detention argue that the nation needs to be able to arrest and jail suspected terrorists without trial, including Americans on U.S. soil, for as long as there is a war on terror. Their argument won, and the measure was defeated by a vote of 200 to 226.