A federal district judge in New York ruled last week that the Defense of Marriage Act violates the Constitution by requiring the plaintiff to pay federal estate tax on her same-sex spouse’s estate, even though opposite-sex spouses are exempt. It follows a string of other rulings striking down the law in a federal appeals court, two federal district courts and a bankruptcy court.

With the Obama administration’s decision in 2011 not to defend the law, that task has been taken up with relish by the Republicans in Congress. Last week in California, their lawyers filed a brief in the United States Court of Appeals for the Ninth Circuit challenging a district court ruling that the law violates the Constitution by denying health benefits to the same-sex spouse of a federal lawyer.

The brief makes the claim that the law’s goals are to maintain consistency in allocating federal benefits and encourage relationships “that most frequently result in the begetting and raising of children.” But in fact, the law thwarts consistency by accepting some state definitions of marriage and rejecting others. And the Republicans offer no real evidence that expanding the definition of marriage to include same-sex spouses affects the ability of opposite-sex couples to marry or have children.

The federal courts that have reviewed this law since 2010 have found that it fails to meet the most elementary test of constitutionality. Under this “rational basis” test, a statute will be upheld — even when groups are treated differently — if the law has some reasonable relationship to a legitimate government purpose.