On Monday, House Republicans are scheduled to weigh in with a federal court in New York on the side of a law called the Defense of Marriage Act.
Big majorities in Congress passed the law 15 years ago to define marriage as being between a man and a woman. Usually, it's the Justice Department that speaks up when federal laws are challenged in court. But in this case, the Obama administration has declined to defend a law it considers unconstitutional.
The decision generated controversy among conservatives and even within the Justice Department.
Gay rights activists are criticizing Colorado Attorney General John Suthers for seeking to uphold the Defense of Marriage Act, which is being challenged in Massachusetts. At issue are federal benefits for same-sex couples.