US-FAA14 CFR 91.3
Responsibility and authority of the pilot in command
Read the official ruleOfficial FAA regulation text (public domain)
(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. (b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency. (c) Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator.
Verbatim text of a US Federal Aviation Regulation (public domain), reproduced for reference — not legal advice and not for navigation. A plain-English explainer may be added later; always rely on the current official rule linked above.