A loophole in the law is a small mistake which allows people to do something that would otherwise be illegal.
例句
It is estimated that 60,000 shops open every Sunday and trade by exploiting some loophole in the law to avoid prosecution.据估计，每逢周日开门营业的店铺有6万家，通过钻法律漏洞躲避检控。
英汉词典释义
n.
漏洞, 空子
They tightened the loopholes in those acts.他们堵住了那些法案中的漏洞。
英英词典释义
Noun
1. an ambiguity (especially one in the text of a law or contract) that makes it possible to evade a difficulty or obligation
2. a small hole in a fortified wall; for observation or discharging weapons