Sentence:  "Doesn't he realize the difference between fiction and fact?” “Not if he doesn't want to,” she said with a short laugh. “Egan makes up his rules as he goes along. He's a <WSD>law unto himself</WSD> out West.” 
Meaning of the word marked with <WSD> tags:  One who flouts the law or conventional wisdom; one who ignores rules or logic to behave according to his or her own standards.