on pain of sth违则受到某种惩罚；违则以…论处，当你想用英语表示因违反某事物而受到某种惩罚，就可以用这个习语来形容。

【例句】
They were required to cut pollution levels, on pain of a 10 000 fine if they disobeyed.
他们被要求降低污染水平，违则罚款1万英镑。

We were forbidden, under pain of imprisonment, to use our native language.
我们被禁止使用母语，违者将被关进监狱。