1. scold somebody or forcefully tell them what to do
lay down the law to your students
This expression means to rebuke or order people about without care for their feelings or opinions. However, it is not always used in a negative context. When a figure of authority, like a boss, parent, teacher etc. 'lays down the law,' it is often done for benefit of the recipient or for the greater good. It can be used in both a social and professional setting, though the latter is more common. A similar expression is 'crack the whip.'