If interviewer contacts your boss when you ask them not to, what do you do then?

One of my co-workers recently applied for jobs at other locations, and requested specifically that his current boss not be contacted. Well, it somehow got back to his boss anyways, and has caused some problems for him. I have never heard of this happening before and I was just wondering if theres anything he can do about this? Seems pretty shady for the interviewer to do.