in the court ruled that the section of doma that limited spousal recognition under federal law to a man and a woman is unconstitutional.

I believe the answer is: United States v. Windsor

In United States v. Windsor, it argued that the law regulating the marriage in united states does not specify that it must be done with the pair of one man and one women. This case is considered as a landmark in united states civil case because it opened up the pathway for same sex marriage.