In this case I’m pretty sure you don’t have to worry! Deciding scope runs every time the command is parsed (and some other times) and “place foo in scope” only applies to that particular scope decision. So, if I’m reading this correctly, this code should automatically stop putting the Pope in scope once Opening Scene ends–after Opening Scene ends, that rule won’t apply, so the Pope never gets put in scope.
As far as saying “Put this particular thing out of scope,” I don’t think it can be done–in a particular round of scope-deciding, once something it’s in scope it stays there. But again, the deciding the scope activity starts anew every time a command is getting parsed.