It has to have been possible for the information to have traveled between the parties normally. In this case, it has to have been possible that a photon would h

It has to have been possible for the information to have traveled between the parties normally. In this case, it has to have been possible that a photon would have traveled between the two. Since the information couldn't have arrived FTL normally due to the everyday causality problems, it also couldn't have passed through this channel FTL.