Gay Marriage Bans

Here's what I don't understand: why isn't someone taking the states that pass gay marriage bans to court? The gay marriage bans clearly violate the separation between Church and State set forth in the United States Constitution. Defining marriage solely between a man and woman is Biblical based (i.e., Church). So, to ban gay marriage by using that definition, the separation between Church and State no longer exists, thus the violation of the United States Constitution.

Now, I know, I'm probably missing something, somewhere but it seems pretty simple to me. If the law (gay marriage ban) violates the separation between Church and State, then the law is illegal. I'm just saying . . .

S