The Federal gov. didn't bring this lawsuit.It's a state's right, the feds need to keep their nose out of it.
Sexual orientation is protected from discrimination just the same as race.As to states passing laws governing race in marriage, that would likely be in-conflict with federal civil rights laws. But sexual orientation has no such protection.
Civil rights extend to all people regardless of gender, religion, race, sexual orientation, age, national origin, and physical or mental disability.