He argued that the congressional authorization to use military force allows such surveillance since intercepting an enemy's communications is a key part of engaging in war.

CNN: Justice Department offers legal basis for wiretaps

In the Hamdi case, the Supreme Court considered the relationship between the current Authorization for Use of Military Force and the Non-Detention Act, which prohibits the detention of a U.S. citizen, except where authorized by an Act of Congress.

FORBES: Following NDAA Debate, Sen. Levin Incorrectly Asserts That AUMF Authorizes Detention of U.S. Citizens

At issue was whether the Authorization for Use of Military Force -- passed by Congress after the September 11, 2001, attacks -- gave the president the power to order the indefinite military detention of an accused terrorist seized on domestic soil.

CNN: 'Enemy combatant' ruling goes administration's way