State Marriage Laws are Constitutional

Of course they are; only one who can't read or a progressive with disdain for the ideals enshrined in the Constitution (by those antiquated old white males) could think otherwise.

Excerpt:

There is nothing in the U.S. Constitution that requires all 50 states to redefine marriage. The only way one can establish the unconstitutionality of man–woman marriage laws is to adopt a view of marriage that sees it as an essentially genderless, adult-centric institution and then declare that the Constitution requires that the states (re)define marriage in such a way. In other words, one needs to establish that the vision of marriage our law has long applied is wrong and that the Constitution requires a different vision. There is, however, no basis in the Constitution for reaching that conclusion. Marriage is based on the anthropological truth that men and women are distinct and complementary, the biological fact that reproduction depends on a man and a woman, and the social reality that children deserve a mother and a father, and states have constitutional authority to make marriage policy based on these truths.