The program has prompted a heated debate about presidential powers in the War on Terror since it was disclosed in December.
The nation's largest organization of lawyers adopted a policy opposing any future government use of electronic surveillance in the United States for foreign intelligence purposes without first obtaining warrants from a special court set up under the 1978 Foreign Intelligence Surveillance Act.
The 400,000-member ABA said that if the president believes the FISA is inadequate to protect Americans, he should to ask Congress to amend the act.
Bush and his administration have defended the warrantless eavesdropping, saying it is needed to fill a gap in U.S. security and is allowable under both the president's constitutional powers and the congressional measure authorizing him to go to war in September 2001.
The ABA has urged Congress to affirm that when it authorized Bush to go to war, it did not intend to endorse warrantless spying.