lay down the law

Verb

 * 1) To promulgate law.
 * 2)  To present the law that applies to a given case.
 * 3)  To authoritatively or dogmatically assert what is permitted or not permitted.
 * 1)  To present the law that applies to a given case.
 * 2)  To authoritatively or dogmatically assert what is permitted or not permitted.