These laws have already been ruled unconstitutional by the Supreme Court in Lawrence v. Texas, so they carry no weight, regardless of laws against sodomy at the state level. This is just politicians trying to appease their socially conservative / evangelical base, especially in light of the gay marriage ruling last year.
Where in the Constitution does it mention the federal primacy over sexual preference? I will wait.
Vince mentioned "federal law", not the Constitution.
Reality check is that states should be remarkably free do do retarded shit like this. That is the beauty of a Constitutional Republic.