slip through the net

(US slip through the cracks)

​

to escape a punishment or be missed by a system that should deal with or protect you

漏网;被漏掉

Once again terrorists have slipped through the police net.

恐怖分子又一次逃脱了警方布下的罗网。

There are laws to protect the mentally ill, but now and then someone does slip through the net.

虽然有保护精神病患者的法律，可是时不时会有人没有被照顾到。