I worked for a very insecure woman once who would not permit what she called "visiting" between employees during work. Which was of course, stupid, unenforcible (I checked with HR) demeaning and unnecessary. Of course, we talked constantly on the phone to each other after hours, and even sometimes at lunch we'd call each other. Unless you work at a very private government facility, this isn't a rule that can happen, more of an idle threat. I have seen many a former employer who'd call and demand that we cut someone's unemployment benefits off because of something they were doing after being terminated, like "speaking badly of their business."