I have only just seen your post.
Whilst it isn't spelt out in the law book, the fact is that a referee can go to the captain of a team and ask him to exert control of all aspects of his team - including spectators, substitutes and players on the field. If no control is created the referee is absolutely entitled to do what ever he deems necessary to ensure discipline remains.
I am implicitly entitled to suggest to a captain that he will be dismissed should a breakdown in discipline occur. The precedent is set in the committal of a 'professional foul' or 'persistent infringement offence'; where the offending player can't be identified, the referee is entitled to dismiss the captain following a general warning being issued.
If in doubt, go to the captain. If this fails, take a view. There is no need to 'make any new laws up', the powers vested in the ref by the existing laws allow this to be possible. 'The referee is the sole arbiter of law and time'.
If any referee or administrator thinks this is incorrect, please post to submit alternative viewpoints.
I hope this clears up where I am on this. Also, I believe most, if not all referees will agree with this.