Is this legal?

A friend of mine at our place of work is having an affair with a married man....only he is separated from his wife, and the divorce is finalized soon. Our boss has recently found out about the out-of-work relationship and has issued an in building restraining order between the two. They aren't allowed even on the same floor in the building. This is weird cuz they have never done anything but said hi or something at work. Is this right that they can do this??? Is it like a form of retaliation since the guy is like legally still married and they are trying to show their disapproval of it or what??