A: Ah, you think you're clever, don't you? Thinking that time travel is all about breaking the rules? Newsflash: it's not. The timeline is a delicate ecosystem, and we can't just go around creating paradoxes willy-nilly. It's like, you know, don't even think about it.
A: Oh, you're one of those fancy-pants physicists, eh? Thinking you can game the system with your fancy principles and equations? Well, let us tell you something: we've got a team of temporal accountants who've been keeping an eye on you. You're not as slick as you think you are. Check your account.