The human said we couldn’t enter while he was alive. So...if we can’t go in while he’s alive...

Not at all. It’s elementary. The human specifically stated that entry is forbidden as long as he was alive. That's tantamount to an invitation when he’s dead

Let those sociologists stuff this in their collective pipe. Puts the kibosh on the deprivation-breeds-antisocial behavior chestnut. This Fowl character has never gone hungry in his life.