It is just a point of logic and reasoning–how do you prove a negative, how do you prove a rule if there can be exceptions–it’s just difficult to do as a matter of logic in a show about magic. So we can look at examples and guess–but the writers can always say “Yeah, you can’t use magic to make someone love you but….surprise, you can steal a heart to make someone THINK they love you!”.
Plus there’s the Adam and Eddy unshameful trolls who fudge their own rules factor: About Greg lying to Emma they said something like– “Oh it wasn’t a lie, because he really expected to see magic.” Ok, fine he knew there was a town, where weird stuff happened, but to see a pirate on his windshield and a man using a fireball…? Streeeeeetch to say Greg expected it. I think it was one of the podcasts.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass