law unto oneself

Idioms  

1. A person who is totally independent, especially one who ignores established rules. For example, You can't tell Marge how to punctuate; she's a law unto herself. [Second half of 1800s]

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Example Sentences

Grizel considered that a woman’s first duty was to charm, and her second,—if a second remained, worth speaking about,—to defy convention, and be a law unto oneself.

From Project Gutenberg