Bailiwick

That's not in my bailiwick.

Sark is part of the English Channel Islands off the coast of Normandy, France. It is a royal fief, part of the Bailiwick of Guernsey, and has its own set of laws based on Norman law, its own parliament, and exchequer.

The Bailiwick of Jersey.

I established the fairly well-understood pattern that affairs of state were not in my bailiwick.

Jack is full of these insights, thoughtful turns of phrase from a character whose perpetual struggle between wastrel and righteous is all too familiar a bailiwick for the universal insecurities of the human condition.