The Ohio supreme court has dismissed a domestic violence indictment because of Ohio's Defense of Marriage Amendment. I expect the gay lobby to soon be arguing that resistance to same-sex marriage is allowing men to beat their girlfriends in Ohio.
Assault and battery are still crimes in Ohio, just as they are elsewhere. What is really peculiar about the law in Ohio and some other states is that the domestic violence lobby has convinced them to punish spousal battery more severely than stranger battery. I think that the idea is that betrayal by a spouse is somehow worse than being attacked by a stranger.
I don't really agree with the premises behind these domestic violence laws, but if you accept them, then the Ohio court ruling is not surprising. The court is merely saying that if the greater penalty is based on the partners being married, then the law requires that they really be married before that greater penalty is applied.
This court ruling is not an unintended consequence. It is merely distinguishing those who are married from those who aren't, and that is apparently what the people of Ohio wanted to do.