We all know that you can extend the half for the taking of a PK. But what if the CR blows his whistle for time and while turning sees his AR frantically indicating a foul (in the penalty area, of course). I was the AR on the other side and was called over to confer. Ignore for the moment the fact that the CR should have seen the foul himself, and if not, made eye contact with his lead AR. He blew the whistle for full time, but based on further information from his lead AR decided that a foul had been committed. Can he then extend time to take the PK? Or was his signal to end the game final, with no going back?
The "foul" occurs when the AR signals. Considering that the signal originated prior to the full time whistle, the referee has an obligation to hear the AR. In this case he accepted his intervention. The referee must allow the PK [in extended time]. Unless he decides that his full time whistle was late.