The issue of sovereignty is a red line that cannot be crossed.

主权问题是一条不能跨越的红线。

《牛津词典》

How for example crossed this ridge anything to push only then cannot knock child, then you must experiment, the practice to be only then good personally.

比如说过这个坎儿什么的怎么推才不能把小孩头磕了，那你得亲自试验、练习才行。

youdao

These Light-line barriers cannot be penetrated or crossed without special Divine dispensation.

如果没有特殊神圣的许可，就不能穿过或跨越这些光带的分界线。

youdao

Even in the new Iraq, said Monam, there are still many "red lines" that cannot be crossed in entertainment.

CNN: Iraq's TV comedy show courts controversy

Perhaps it should have been staffed by Latinos, who cannot see a Great Divide at all: only bridges to be crossed, chances to be seized, another day's march along the road to completing the world's greatest multicultural experiment.

ECONOMIST: A minority worth cultivating

Even if you believe that the president crossed the line in his Jones' deposition, you cannot conclude that he should be removed for it.

CNN