You seem to be overlooking the point. Would it be morally permissible for me to scribble down arbitrary rules and enforce them on you if I had an army with which to ensure your compliance?

Laws are just arbitrary rules decided on by a small group of people, much like they were with Kings and their inner circles. Laws are enforced in much the same way too - there's no practical difference between getting assaulted by the King's Guard and getting assaulted by men in blue costumes.