He was on TV condemning it. Pretty much like Desh said.
Which is the game. They run it, he complains about it. They run it anyway. He gets credit for "denouncing" it. He reaps the benefit of the negative message and his denouncing it and their running it anyway becomes a news story in and of itself and the cable news shows run the ad for free ad nauseum. It's perfect.
If this was a 527 I could understand the argument that he can't do anything about it, but this is the state GOP. Surely the GOP presidential candidate and the RNC have some levels they can pull other than mealy-mouthed condemnations to get the ads not to run and surely they could do so behind closed doors.