Getting an offer from someone else is not violation of contract (or at least not any basic general employee contract that I've ever seen.) But if they entertain this offer and enter into negotiations for salary etc, I'd say that's a good reason to fire them. It's the other employer's right to OFFER it to them, but for the employee to pursue would be grounds for termination as far as I am concerned. If they were doing it purely for strategic purposes (to find out what competitors are paying, etc) and they let their current boss know, then great. If not, I'd say they are being sneaky and get rid of 'em.
