The "dual sovereignty" doctrine allows a federal prosecution of an offence to proceed regardless of a previous state prosecution for that same offence and vice versa because "an act denounced as a crime by both national and state sovereignties is an offence against the peace and dignity of both and may be punished by each". The doctrine is solidly entrenched in the law, but there has been a traditional reluctance in the federal executive branch to gratuitously wield the power it grants, due to public opinion being generally hostile to such action.