.... Laws against gay marriage ....There are no laws against gay marriage
There are laws that define what a marriage is, and what rights and privileges are granted to a married couple. A marriage is a union between a man and a woman. If you don't want to have that, don't get married.
As I said, an analogous law concerning bah mitzvahs, if you want to construct such an analogy, would be a law that required bah mitzvahs to be performed for anyone, regardless of their religious beliefs, and a that required the privileges and benefits of bah mitzvahs to be conferred on anyone, not just on those who believe in the Jewish faith.
Maybe you have an aversion to logic, or maybe just to the obvious, but if the law defines marriage in a way that precludes gay marriage, there is a law against gay marriage.
I'm simply bewildered that that even needs to be explained.