The Obama Administration is bailing out on the Defense of Marriage Act. That’s the 1996 federal law that defines marriage as the union of a man and a woman.

For advocates of same-sex unions, the announcement that the Administration would no longer defend the law as constitutional came as very good news. But for Congressional leaders, it came as a surprise.

Last week, those leaders received a six-page letter from Attorney General Eric Holder announcing the administration’s decision to switch sides on the issue. Holder’s letter made it clear: the decision to abandon the Defense of Marriage Act in court was made personally by President Obama. The President and his lawyers now and henceforth will assert that part of DOMA, as the bill is called, is unconstitutional.

The awkwardness of this situation is extreme. For nearly two years, the Obama Justice Department has acted as if it were just fine representing DOMA in court. Moreover, the president has repeatedly proclaimed his embrace of the traditional definition of marriage. Indeed, in a lengthy answer to Pastor Rick Warren at a candidate forum in California, Mr. Obama went so far as to say it was a “sacred union” between a man and a woman.

Apparently it is sacred no more.

The truth is that the Obama Justice Department has slowly undermined DOMA from the start. Legal critics across the political spectrum have pointed out that, in court filing after court filing, the Administration has refused to cite the leading arguments and court decisions that buttress the case for DOMA. Holder’s lawyers have refused to cite procreation and the public interest in promoting intact families as a rational basis for the law. They have omitted precedents, including a binding Supreme Court decision on same-sex marriage in 1972, that other courts have relied on ever since.

In reality, then, the administration decided to abandon DOMA years ago. Last week’s announcement merely reflected a decision to drop the pretense that it was defending the law.

However, the decision to openly switch sides comes midstream in the judicial process. That creates real uncertainty about who will represent the Congress of the United States and the law before the courts.

Our judicial system depends completely on a genuine adversarial process. The courts do not accept controversies unless they are just that: important legal matters about which the contending parties deeply disagree. This holds for criminal cases as well as for issues of statutory and constitutional law. When one side of a case is actively helping the other, or putting up a token defense, the courts and the people of the United States suffer a grave disservice.

Even more offensive is the fact that, while serving up this legal surrender, the President and his team are slandering millions of Americans who clearly disagree with redefining marriage. The Justice Department is arguing a legal standard, asserting that there is no rational basis for traditional marriage. This essentially equates proponents of DOMA with irrational bigots. It’s slander – and slander with the odd effect of charging President Obama with bigotry for the view he claims still to hold (though one suspects he is “evolving”).

Marriage is indeed a sacred union. But a sacred trust is at issue here as well. While President Obama is clearly entitled to his own view of the constitutionality of laws passed by Congress, he has taken an oath to ensure that the laws are faithfully executed. “Executed” here does not mean killed. His action in abandoning DOMA in this on-off and offensive manner lowers the bar of good government dramatically. Even the Washington Post, which liked the Holder letter’s substance, thinks this maneuver may come back to haunt Obama when his political opponents hold power again.

Fortunately, there is a way out of this mess that has some integrity. The Justice Department plans to ask the federal courts to allow full and fair participation by Congress in defending its own law. Congress can and should swiftly accept that invitation and provide the federal courts with the best arguments by the best lawyers available.

The Defense of Marriage Act is a crucial piece of legislation. It safeguards traditional marriage and the rights of states not to be forced to copy each other’s experiments with the family. It deserves the skilled advocacy of top-notch attorneys. At least now we know it never had a prayer of getting that from Team Obama.

Chuck Donovan is a senior fellow at The Heritage Foundation.