A more thorough explanation:

Petite policy is a rule created by the Department of Justice that prohibits a federal prosecution after a previous state or federal prosecution based on the same acts, unless certain conditions are met. These conditions include:

1. Approval by the Assistant Attorney General
2. A substantial federal interest supporting the prosecution
3. The previous prosecution failed to vindicate the federal interest
4. There is sufficient evidence to sustain a conviction

The purpose of this policy is to protect individuals from multiple prosecutions and punishments for the same act or transaction, promote efficient use of Department resources, and promote coordination and cooperation between federal and state prosecutors.

For example, if someone is charged with a crime in a state court and is found guilty, the Petite policy would prevent the federal government from prosecuting them for the same crime unless the conditions mentioned above are met. This prevents individuals from being punished twice for the same crime and ensures that federal resources are used effectively.

The Petite policy was established in the case of Petite v. United States, 361 U.S. 529, 80 S.Ct. 450 (1960), and is included in the United States Attorneys' Manual § 9–2.031 (Sept. 1997).