"If I hear the word betray one more time ..." he started. He narrowed his eyes at her as he folded up the map. "Don't you think that if I had betrayed them, James Potter wouldn't be around to talk to you right now?" He let her ponder that for a moment.
Sirius shook his head. "I don't make the rules, Susan, I only enforce them. In the privacy of my office here, as I hope I've demonstrated, you're always welcome to ask questions or talk. However, that's inside the walls of this office, of this school, where Albus Dumbledore still manages some kind of control. But after you've finished here? It's even worse out there, and you need to understand that."