A outlaw is person declared as outside the protection of the law. In pre-modern societies, the criminal is withdrawn all legal protection, so that anyone is legally empowered to persecute or kill them.
The metaphor that Cara uses is that they’re being charged for “killing time together”.
She mentions a couple of famous outlaws, Bonnie Elizabeth Parker and Clyde Chestnut Barrow aka Bonnie and Clyde.