Lay down the law: to say something or give an order in a way that says "you will obey me or accept my word without argument or question !"
定规矩： 用“你不许争论或质疑地听从我或接受我的话”的方式做出指示或下达命令
 
"The way my employees are behaving is terrible," Grouch grumbled. "I'm going to lay down the law and tell them to concentrate on their work."
 “我的员工的行为方式表现太糟糕了”Grouch抱怨，“我要制定规矩，让他们专注于他们的工作。”