I usually find the Washington Post’s house editorials on legal issues (unlike those of the New York Times) to be well within the range of sensible commentary, whether or not I agree with them. Not so with today’s outlandish editorial arguing that the application of the federal Defense of Marriage Act—specifically, of its provision that prohibits the federal government from treating as a marriage a same-sex relationship that a state recognizes as a marriage—to plaintiffs in a federal lawsuit in Massachusetts violates the Equal Protection Clause of the Constitution.

The editorial asks whether DOMA’s various purposes are rationally served by the denial of federal benefits to the plaintiffs. The easy answer to that question is twofold. First, the relevant legal question, under Equal Protection case law, is whether DOMA generally is rationally related to a legitimate government purpose, not whether a particular application can be shown to be. Second, it is entirely reasonable to believe that DOMA’s purpose of defending traditional marriage would in fact be undermined by any instance of the federal government’s treating a same-sex relationship as marriage.

The editorial disingenuously maintains that it is seeking a narrow result, applicable only to the plaintiffs in the lawsuit. But there is nothing in its sloppy reasoning that would be so confined. Its illogic would wipe out DOMA.

Even more recklessly, the editorial suggests that President Obama “should consider whether this is one of those rare instances where the Justice Department declines to defend a [federal] law.” I have no concerns that incoming Solicitor General Kagan would adopt such a foolhardy course (though I certainly have concerns, given her extremist rhetoric about the “Don’t Ask, Don’t Tell” law, that she would not mount a vigorous and effective defense of DOMA).