Under the latter approach, the president would assert that as the head of the executive branch and commander in chief, his prosecutorial discretion and wartime powers would allow him to lawfully bring detainees into the United States for trial or to transfer them to other countries as he sees fit.

It remained unclear whether the administration would actually carry out a detainee transfer despite the restrictions, or whether it would merely assert, as an abstract matter, that Mr. Obama had the authority to do so.

In 2002, under President George W. Bush, the Justice Department’s Office of Legal Counsel wrote that Congress has no power to limit the transfer of detainees because “the president has plenary constitutional authority, as the commander in chief, to transfer such individuals who are captured and held outside the United States to the control of another country.” The Bush administration rescinded that memorandum five days before leaving office.

During that era, Mr. Obama and many future members of his legal team criticized the Bush administration as taking too sweeping a view of executive power. They also criticized Mr. Bush for his frequent use of signing statements to claim a constitutional right to override laws.

Mr. Bush attached such statements to about 150 bills during his eight years in office, challenging about 1,200 provisions — around twice the number challenged by all previous presidents combined. Among the most contentious was an assertion that he had the power to lawfully override a statute banning torture.

In 2006, the American Bar Association declared that presidents should veto legislation they view as flawed rather than issue signing statements, which the group portrayed as “contrary to the rule of law and our constitutional separation of powers.” One member of the Obama legal team, Harold Koh, the State Department legal adviser, was a member of a task force that developed that declaration.

But several other future members of the Obama legal team argued at the time that signing statements were lawful and appropriate so long as the president invoked only mainstream legal theories. Mr. Obama adopted the latter approach, pledging greater restraint.

Early in his presidency, he issued several signing statements that made relatively uncontroversial challenges. But he has not issued any since October 2010, when lawmakers of both parties expressed outrage over a statement he attached to a bill saying that he could disregard requirements imposed on certain negotiations with international financial institutions.