nulla poena sine lege
From Latin, literally, "no penalty without law," a legal principle that a person cannot be punished for an action if that action is not prohibited by law. The company's lawyers successfully argued that their tax practices, however unsavory to the government, were not expressly prohibited by existing laws, and therefore the case against them should be thrown out on the principle of nulla poena sine lege.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.