lay down the law
US /leɪ daʊn ðə lɔː/
UK /leɪ daʊn ðə lɔː/

1.
menetapkan undang-undang, memberi arahan
to tell people what they must do, without caring about their opinions
:
•
The new manager immediately laid down the law about punctuality.
Pengurus baru segera menetapkan undang-undang mengenai ketepatan masa.
•
My parents always lay down the law when it comes to my curfew.
Ibu bapa saya sentiasa menetapkan undang-undang apabila tiba giliran saya.