A phrase used to describe someone who acts independently of what is normal or expected. Julie has always marched to the beat of her own drum. She's a law unto herself.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a law unto yourself
COMMON If you describe a person or organization as a law unto themselves, you mean that they do what they want, ignoring laws, rules, or usual ways of doing things. He does his work well but in an unconventional way. He is truly a law unto himself. Most athletic departments are pretty much a law unto themselves — unaccountable in terms of where this money goes.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
a law unto (oneself)
A totally independent operator: An executive who is a law unto herself.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.