Isabelle Lightwood: You know what, Lydia? You’re no better than Valentine. But at least he had the guts to tell Downworlders to their faces he wanted them all dead. You… hide behind the Law.

Lydia Branwell: I don’t hide behind it, Isabelle. I simply follow it. Because it guards against one very important thing. Shadowhunters fighting other Shadowhunters.

From Shadowhunters – Season 1 Episode 10: ‘This World Inverted’ (1×10)