There is no precedent for a disaster of this scale.

这种规模的灾难是空前的。

《牛津词典》

There's no precedent for this.

向无此例。

《新英汉大辞典》

But there really is no precedent for Mr. Summers’s role.

但是，事实上，萨默斯所担当的角色并无先例。

youdao

There has been no precedent in a similar case in Israel since the 1980's.

BBC: Palestinian stone thrower to appeal murder conviction

There is no precedent for such an action, and the judges might refuse to recognise it.

ECONOMIST: Another problem for Pervez Musharraf

There is no precedent in Scotland for force feeding a prisoner on hunger strike.

BBC: New date set for Moors Murderer Ian Brady's tribunal