Put (one's) foot down

Translation of "put (one's) foot down" into Russian

проявить твердость, настоять на своем

She had to put her foot down when her kids wanted to stay up late.

Ей пришлось настоять на своем, когда дети хотели лечь спать поздно.

To assertively enforce a decision or take a firm stand, especially after a period of indecision or leniency.