This essay argues that federalism played a profoundly important role in the Supreme Court\u27s decision in United States v. Windsor, which struck down the federal Defense of Marriage Act. Arguments to the contrary have failed to appreciate how Justice Kennedy\u27s opinion employed federalism not as a freestanding argument but as an essential component of his rights analysis. Far from being a muddle, as many have claimed, Justice Kennedy\u27s analysis offered one of the most sophisticated examples to date of the interconnections between federalism, liberty, and equality