In exchange for the release of U.S. Army Sgt. Bowe Bergdahl, the U.S. agreed to free five Taliban commanders from the military detention center at Guantanamo Bay, Cuba. They were among the Taliban’s most influential commanders. (Tom LeGro and Natalie Jennings/The Washington Post)

Back when Barack Obama was a presidential candidate who boasted his background as a professor of constitutional law, he frequently criticized President George W. Bush for what Obama said was a “clear abuse” of executive power.

As president, Obama is being accused of doing the same, albeit not as frequently.

The issue at hand is his use of “signing statements,” official pronouncements in which a president offers his interpretation of legislation that he is signing — and in the modern era, sometimes announces that he feels free to disregard it.

While Obama has not issued as many signing statements as Bush did, many say he employs them in much the same manner.

“The difference is really with volume, not in kind,” said Kevin Evans, a Florida International University professor who has researched the practice of presidential signing statements. “Senator Obama had a very different view than President Obama.”

The latest — and potentially hottest — flash point involves Obama’s decision over the weekend to trade the release of Army Sgt. Bowe Bergdahl, the sole remaining U.S. military prisoner of war, for that of five Taliban commanders who were being held at the detention center at Guantanamo Bay, Cuba.

Current law, signed by Obama in December, stipulates that the defense secretary must notify relevant congressional committees at least 30 days before transferring anyone from Guantanamo Bay and provide assurances that those released would not be in a position to again threaten the United States or its interests.

Obama did not send such a notice to Capitol Hill until Monday — two days after the detainees were sent to Qatar, where they will live for at least the next year, in circumstances that neither the administration nor the emirate has explained publicly.

That Obama should ignore the notification provision, which was part of the 2014 National Defense Authorization Act, is not entirely a surprise.

In the signing statement with the law, Obama declared that he thought the requirement was potentially unconstitutional.

“The executive branch must have the flexibility, among other things, to act swiftly in conducting negotiations with foreign countries regarding the circumstances of detainee transfers,” Obama said.

In the case of Bergdahl’s release, administration officials have argued, life-or-death circumstances required fast action.

That has not quieted the criticism from Capitol Hill.

“Our joy at Sergeant Bergdahl’s release is tempered by the fact that President Obama chose to ignore the law, not to mention sound policy, to achieve it,” House Armed Services Committee Chairman Howard P. “Buck” McKeon (R­Calif.) and Sen. James M. Inhofe (Okla.), the ranking Republican on the Senate Armed Services Committee, said in a joint statement.

Senate Intelligence Committee Chairman Dianne Feinstein (D-Calif.) said her panel should have been notified before the transfer. Past proposals for prisoner swaps with the Taliban raised “considerable concern,” she added.

The practice of issuing signing statements goes at least as far back as President Andrew Jackson, who in 1830 issued one stipulating that he would not extend beyond Michigan territory an $8,000 road that Congress wanted to build from Detroit to Chicago.

But they were relatively rare until Ronald Reagan began using signing statements as a means of asserting the power of the executive against the legislative branch.

George W. Bush used signing statements to challenge about 1,200 provisions of 172 laws he signed — twice as many as all his predecessors combined, Evans said.

In 2006, a 10-member panel of lawyers and legal scholars assembled by the American Bar Association criticized him for it and wrote: “The President’s constitutional duty is to enforce laws he has signed into being unless and until they are held unconstitutional by the Supreme Court or a subordinate tribunal. The Constitution is not what the President says it is.”

If a president objects to something in a bill, the ABA group argued, he should veto the whole thing.

Obama was among the critics of Bush’s use of signing statements.

Although he did not pledge to abstain from using signing statements, Obama said he would wield the power more judiciously.

“I will not use signing statements to nullify or undermine congressional instructions as enacted into law,” he wrote in response to a December 2007 questionnaire from the Boston Globe. “The problem with this administration is that it has attached signing statements to legislation in an effort to change the meaning of the legislation, to avoid enforcing certain provisions of the legislation that the President does not like, and to raise implausible or dubious constitutional objections to the legislation.”

As president, Obama has issued close to 30 signing statements; in the 2013 Defense Authorization Act alone, he challenged more than 20 sections of the law. Among the challenges have been assertions of his power to close Guantanamo Bay, for instance, and to disregard whistleblower protections.

White House spokesman Josh Earnest said Obama’s decision not to comply with the 30-day notification requirement in the Bergdahl case was “completely consistent with the objections we’ve raised about the president’s ability to manage the nation’s foreign policy.”

Earnest added that Obama’s overall approach to issuing signing statements has been “consistent with what he campaigned on.”

Others disagree.

Obama’s use of the practice has “been indistinguishable from Bush. The volume is a little less,” said Bruce Fein, who was a member of the ABA panel. “His conception of executive power is equally as grandiose as Bush.”

And according to a January 2012 report by the nonpartisan Congressional Research Service: “While the frequency with which the Obama Administration has asserted constitutional objections to enacted statutory provisions represents a departure from previous administrations, the types of objections within the signing statements that the President has issued have generally mirrored those of previous administrations.”

But, as with everything else in Washington, reaction generally takes a party line.

“When Bush was issuing signing statements, the Republicans didn’t care. When Obama was doing it, Democrats didn’t care,” Fein said. “And that is how power accrues to the president.”

Alice Crites contributed to this report.