Any attempt to federally legalize same-sex marriage would be a direct affront to the founding principals of the country. Not to mention a blatant violation of the Tenth Amendment (not that anybody in the federal government cares). It should be left up to the states, not the federal government.
See what brittain has to say about the issue first--both of his points are what is desired action on the part of the federal government, neither of which is a "blatant affront".
Also, the federal judiciary absolutely has the right to override state laws and constitutional amendments in this regard as they violate the Constitution as well, specifically the 14th amendment.