That is completely unacceptable if you are outside the penalty timeframe and actually does not sound legal, but what do I know. I would be screaming at the top of my lungs if they tried it on me and I hope you are also in the high decible range right now. Complain, complain, and complain some more. Let them know your feelings and what you have done for them and what the results will be from the bad publicity they will be receiving from this unreasonable stance. Your TA should also be screaming at them for this behaviour. Please let us know what the end results are.