Actually I think what you said was clever. It's very hard for an addict whose trying to avoid consequences, understand that it is exactly what you want him to experience. On top of that it's hard to understand why your mother or anyone else would want you to experience those consequences. I think it's harsh to just not pay for a lawyer and not explain your reasoning. (not to us, but to him maybe) Your explanation was a very good example of what happens when someone bails you out all the time.
My feeling is the hang up was percipitated by his really hearing your message. You used an example that relates directly to him. I know when my mom has a good reason for doing something, I can't argue with it and it makes me mad. If there was no logic to it, I would continue to fight for my cause.