Anyone who has ever tried to argue for the preservation of the traditional definition of marriage has probably had to listen to the proclamation that "marriage is a fundamental right" -- a right that you are then claimed to have denied to same-sex couples. So, to answer whether we do in fact have a fundamental right to marriage, we must, as usual, first define the terms we use. If by "marriage" one means that people have a right to love and grow old with whomever they like, then if we do not already have a fundamental right to such aspirations, we should; and in America, for all intents and purposes, we do. Gay and straight people alike are completely free to make whatever religious or personal commitments of love that their heart desires.
But if by "marriage" one refers to government recognition and encouragement of a couple's relationship, then no right ever existed nor should it. All the same, let's, for argument's sake, assume that couples do in fact have a right to "marriage" and that "marriage" means the right to not just love whomever you like, but to receive government treats as well. In a democracy, "We the People" still need to define who is entitled to get "married." Only they have access to this fundamental right. And as of right now, the democracy has overwhelmingly decided that this only applies to heterosexual couples.
Yet, for the same-sex special-interest groups, that is rarely if ever enough. Every time they lose at the ballot box, these groups take their cause to the oligarchial courts. These activist judges then make use of the vaguer language from decisions like Loving v. Virginia (1967) to make the case that the government must encourage all types of relationships in the same exact way. That is to say, they argue that marriage is a fundamental right and thus denying marriage to same-sex couples violates the constitution.
These courts then order the democracy to change the law to how they see fit. Nevertheless, even on their own constitutionally-delusional terms, to do so they must necessarily extend the definition of "marriage" to include same-sex relationships. Without such an extension, the fundamental-right status – the status they use as a sword to pierce the democracy -- disappears; only "marriage" is a fundamental right.
So why do people not have an issue with the courts taking these radical steps? It is likely because, unfortunately, this sleight of hand fools far too many otherwise intelligent people.
Maybe an example will help: "Parents" also have a fundamental right. Theirs is the basic right to dictate the way their kids are raised. However, if you went to your neighbor's house and declared you -- not just the father and mother -- have a fundamental right to dictate their kid's upbringing, I hope you agree, you would be nuts. This would be true even if you paraded in the streets with a bunch of rainbows and leather, screaming that the definition of "parents" has "progressed" and now includes neighbors as well. Neighbors, according to the definition agreed to by society, have no fundamental right; surely most would agree that the courts have no authority to extend the definition of "parents" to give neighbors that right, right?
So, too, there is no fundamental right for anyone, in any situation, to get legally married. They must meet society's definition of "marriage," which is now just a man and woman. Of course, one can try to persuade society to change that through democratic channels. Until that occurs, however, the constitution and of course, the courts, have nothing to say about the issue. But that doesn't stop them. Too bad, democracy was good while it lasted.