You can play as the Chancellor of Rheinland but if no one listens to you, what's the point?
Much the same for this Crime Boss position.
Del has earned respect from people for his choices and his efforts. If you respect him enough then of course you will follow the RP rule. If you don't, you won't follow it. Even if you hate him you can still respect him remember.
In any case, as Del said, he didn't intend enforcing this. If you respect him enough in his Crime Boss position, then you will follow this law. (As is true in RP. If there was an idiot yelling that he was a crime boss and spouting random laws, you wouldn't listen to him in real life, or RP. Same goes for here)