He's not being prescribed. When the Tv goes off, if he is awake, he can put it back on again. Also, does he need the Tv on that loud? On many newish models you can set a maximum that the volume can be turned up to however much you press the volume on the remote. I know its sneaky but if the neighbours complain to the council (as they well might) then he will have more serious problems to deal with.
he might not be turning it up on purpose? Some channels are noisier than others and seem to get noisier late at night, also he may be doin something like turning up the sound instead of changing the channel which my Mum used to do.