
A law that automatically terminates the agency or program it establishes unless the legislature expressly renews it. For example, a state law creating and funding a new drug rehabilitation program within state prisons may provide that the program will shut down in two years unless it is reviewed and approved by the state legislature.
Found on
http://www.nolo.com/dictionary/sunset-law-term.html

a statute that includes provision for automatic termination of a government program, agency, etc., at the end of a specified time period unless it is reauthorized by the legislature.
Found on
https://www.infoplease.com/dictionary/sunset-law
No exact match found.