DOMA did at least concern federal benefits that states don’t naturally have the authority over, so it wasn’t clearly a 10th Amendment violation.
It defined marriage as between a man and woman, something you, Ferris and many other states rights conservatives have repeatedly said was up to the states to decide. If gay marriage is truly up to the states to decide, I don’t know how you could justify a federal law that defines marriage. I think I even brought up federal benefits to argue that the feds had to have some say over marriage, I forget the argument that you and/or Ferris used against me. If it weren’t so hard to search this site, I’d try to find the conversation.
In many areas I would defer to the states. I still think DOMA went too far and infringed on state authority. But I recognize the sincere argument, that you previously made, that a person can support state authority and also limited federal action without offending the 10th Amendment. Not all states’ rights people are absolutist (I’m not). The fact I can recognize a sincere argument doesn’t mean I agree with it.