Lawyers for the Republican majority in the House of Representatives are disputing on several fronts a ruling by the U.S. Court of Appeals for the Second Circuit that the Defense of Marriage Act unconstitutionally discriminates against same-sex married couples. But they argue that the issues in the case can be distilled to a few fundamental legal principles.

“Although the passions that surround the issue of same-sex marriage undoubtedly run high, the issue before this Court is quite narrow,” Congress’ attorneys argue in a brief submitted to the U.S. Supreme Court last week in Windsor v. United States, 12-307. “Assuming that states remain free either to recognize same-sex marriages or retain the traditional definition, the question here is whether the federal government retains the same latitude to choose a definition for federal-law purposes, or whether instead it must borrow state-law definitions as its own, recognizing same-sex marriages of U.S. citizens residing in Massachusetts (because Massachusetts does) but not same-sex relationships of U.S. citizens residing in Virginia (because Virginia does not).”