Its only forbidden because people seem to think they can walk into my garden and take my apples for free. Well I am sick of it, so no more fruit for anyone!
Why not throw them out of the garden forever? That's not harsh at all. Also, curse them with the ability to die and have their corpses rot, too. That'll teach them.

By the way, I heard you're making some sort of punishment apparatus. May I suggest... something to do with fire?