Zero writes a memo, and the law is effectively changed for the whole country.
We are, indeed, in a dictatorship.
The statutory provision establishing minimum wage and overtime exemptions for executive and other white collar employees, section 213 (a)(1) of the Fair Labor Standards Act, specifically authorizes the Secretary of Labor to define those employees subject to the exemption and to modify those definitions from time to time. So your beef here is with Congress, for writing laws which turn over legislative power to the executive branch.