WASHINGTON » When President Barack Obama decided that his administration would no longer defend the Defense of Marriage Act in court, he was presented with an obvious question with a less obvious answer: Would he keep enforcing a law he now deemed unconstitutional?

A debate in the White House broke out. Some of his political advisers thought it made no sense to apply an invalid law. But his lawyers told Obama that he had a constitutional duty to comply until the Supreme Court ruled otherwise. Providing federal benefits to same-sex couples in defiance of the law, they argued, would risk a furor in the Republican House and theoretically even provoke articles of impeachment.

Two years later, that decision has taken on new prominence after Chief Justice John G. Roberts Jr. accused Obama from the bench Wednesday of not having "the courage of his convictions" for continuing to enforce the marriage law even after concluding that it violated constitutional equal protection guarantees. The chief justice’s needling touched a raw nerve at the White House, where the president’s team argued he had done the only thing he could do.

Other presidents have enforced laws that they no longer defended in court, including former President George W. Bush, whose acting solicitor general, a man named John Roberts, once asked the Supreme Court to overturn a minority preferential program at the Federal Communications Commission.

But the fuss this week underscored the awkward balancing act for Obama, whose administration refused to refund federal estate taxes to an 83-year-old lesbian even though he thought it was wrong not to.

"I’m sure there are people in our community who would agree with the chief justice that the president should go farther and not enforce" it, said one leader in the fight for same-sex marriage, who declined to be named while the case was pending. But leaders in the fight came to accept the decision "because without enforcement, there’s no means to challenge the law" in court.

The decision to repudiate the Defense of Marriage Act came two years into Obama’s term. Although the Justice Department had defended it in the past, the courts were being asked to examine the law for discrimination under a tougher standard.

Some at the Justice Department argued that the administration should continue to defend the law. But Attorney General Eric H. Holder Jr. decided the law did not meet the higher standard. He talked the issue through with Obama, who once taught constitutional law at the University of Chicago, and the president agreed. They would no longer defend the law against court challenges.

But administration lawyers researched the matter and concluded that the president should still enforce it while the courts deliberated. Even then, not every lawyer agreed. One Justice Department lawyer thought the administration should refuse to enforce the law as well.

The question comes down to the president’s obligation under Article II of the Constitution to "take care that the laws be faithfully executed." The meaning of that has been debated at least back to 1860, when the attorney general at the time concluded that the president could disregard a law purporting to appoint a government officer because it was unconstitutional.

The debate played out into the next century. After President Woodrow Wilson refused to comply with a law preventing him from removing postmasters without Senate approval, the Supreme Court struck down the statute in 1926 as an encroachment on executive power in a case that was seen as implicitly agreeing that a president is not required to execute unconstitutional laws.

A 1977 opinion by the Justice Department’s Office of Legal Counsel under President Jimmy Carter concluded that a president could ignore a statute he considered unconstitutional, depending on the circumstances. A memorandum by the same office in 1994 said the president could do so when the law tried to improperly limit executive power or when it was "probable that the Court would agree with him."

But when a reasonable argument could be made on the other side, lawyers said, the president should still comply until the courts rendered a definitive verdict. That was what President Bill Clinton did in refusing to defend in court a 1996 law expelling all HIV-positive soldiers from the military even as he said he would enforce it. Congress ultimately repealed the law.

That was a precedent that Obama’s lawyers leaned on in 2011 as they made their determination on the Defense of Marriage Act.

The decision prompted a debate outside the White House as well. Neal Devins and Saikrishna Prakash, law professors at the College of William and Mary and the University of Virginia respectively, wrote in The Columbia Law Review that given his belief that the law was unconstitutional, Obama "should neither enforce nor defend it."

The issue was raised again by the chief justice Wednesday during oral arguments on a challenge to the law.

"If he has made a determination that executing the law by enforcing the terms is constitutional, I don’t see why he doesn’t have the courage of his convictions" and decline to enforce it, Roberts said, "rather than saying, ‘Oh, we’ll wait ‘til the Supreme Court tells us we have no choice."’

Sri Srinivasan, the deputy solicitor general representing the administration, said that was an option but Obama had decided not to take it.

"That was out of respect for the Congress that enacted the law and the president who signed it, and out of respect of the judiciary in saying what the law is," he said.

Walter E. Dellinger III, the former assistant attorney general who wrote the 1994 memo, defended Obama’s decision.

"He does have the courage of his convictions," Dellinger said in an interview Thursday, "because he’s conveying his convictions to the court, and his convictions include that the court has a proper role in deciding constitutionality."

Charles Fried, who was solicitor general under President Ronald Reagan, said that while there are extraordinary situations where a president could refuse to enforce an unconstitutional law, this was not one of those.

"That would be civil disobedience," Fried said. "I don’t think he’s got the right to do that."

Still, Fried said Obama should not have refused to defend the case in court on the same principle that the executive, except in the rarest circumstances, should uphold the law. If he felt uncomfortable doing so, Fried said, then the president should have hired an outside counsel who would be willing to offer a defense.

"I think he was wrongly advised," Fried said. "I think it was looking to make a political statement and feeling an unwillingness to defend something that he thought was wrong. I understand that. But he could have dealt with that problem and gotten the job done."

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