law unto oneself

noun3

1. •
   One who is free from the constraints of law or rules.

   • If you take away the Law, all things will fall into a Confusion, every Man will become a law unto himself; which, in the depraved Condition of Human Nature, must needs produce many great Enormities. — 1707
2. •
   One who flouts the law or conventional wisdom; one who ignores rules or logic to behave according to his or her own standards.

   • "I've made up my mind. I'm going to do dairy work, and it's not a bit of good your trying to talk me out of it!" [...] Dilys had always been more or less a law unto herself. — 1916
3. •
   (old-fashioned) One who is lawful in the absence of an enforced law; one who behaves with integrity.

   • For when the Gentiles which haue not the Law, doe by nature the things contained in the Law: these hauing not the Law, are a Law vnto themselues. — 1611