Gay marriage, isn't this a religious issue?:
Civil marriage (i.e. the license you get when you get married) is not religious in any way, shape or form. It is in its very nature controlled by the government and government thus has the right and responsibility to define it. I don't think it should do so in a way that blatantly discriminates against a group like homosexuals, but it is most certainly within the government's prerogative to define marriage. If you find a church that agrees to, you can have a wedding ceremony to whomever or whatever you like, but only the government can decide if the government is going to recognize it.