Funnily enough, assuming that Vampires can only enter a house if they are invited, being able and allowed to enter the house are, in this case, equivalent.

The worst thing about this is that the English teacher is wrong too - common usage dictates that this is a perfectly acceptable form of request.

The vampire’s ability to enter (whether he can come in) depends on his permission to enter (whether he may come in). So he’s right.

He’s clearly already inside the house tho