loophole

loop·hole /ˈlu:pˌhoʊl/ noun

plural loop·holes

[count] : an error in the way a law, rule, or contract is written that makes it possible for some people to legally avoid obeying it
▪ She took advantage of a loophole in the tax law. ▪ a tax loophole ▪ His attorney has been hunting/searching for a loophole that would allow him to get out of the deal. ▪ tried to close/plug a loophole in the new legislation