I think you're just screwed on this one.

It would, of course, be well to point out to the execs that this is not quite the same as having Fred and the little lady over for beer and football, but it's not likely that it will do any good. The powers that be would have to admit they were wrong, and there are not many things more petty than a minor "power-that-be!" Maybe a petty bureaucrat, but I'm not sure.

You could pursue all this through labor law, but doing so is not only overkill, it's probably professional suicide. I really hate it, but there may not be any good choices here.

Having said that, I will point out that non-fraternization rules have a good basis. Familiarity really does breed contempt, and the general rule has a good reason for existing. Of course, the downside is that "general rules" and policies tend not to actually fix anything.

Good luck and keep us posted.