A more thorough explanation:

A peremptory writ of mandate, also known as mandamus, is a type of judicial order that compels a government body, government official, or lower court to perform an act or stop an action. This is done when the court finds that an official law, duty, or judgment requires them to do so. It is different from an alternative writ of mandate because the act that the court compels has already been established by a lower court or government body.

For example, in Sholtz v. U.S., the Circuit Court of Appeals, Fifth Circuit affirmed the issuance of a peremptory writ of mandate which required Florida state officials for the treasury department to pay a judgment, their liability therefor a lower court had established. As another example, the California Superior Court in California Building Industry Assoc’n v. State Water Resource Control Bd. issued a peremptory writ of mandate to compel the State Water Resource Control Board to halt the implementation of certain environmental standards where the invalidity of the standards has already been established.

Courts usually require that the defendant has notice of the petition of the writ and an opportunity to present their arguments. For example, California Code of Civil Procedure § 1088 requires that “[w]hen the application to the court is made without notice to the adverse party, and the writ is allowed, the alternative must be first issued; but if the application is upon due notice and the writ is allowed, the peremptory may be issued in the first instance.” Additionally, the California Court of Appeal in Campbell v. Superior Court illustrates an instance where defendants to a peremptory writ of mandate had the opportunity to present new evidence at a hearing to adjudge whether the writ should be issued.

Overall, a peremptory writ of mandate is a powerful tool that courts can use to ensure that government bodies and officials follow the law and fulfill their duties.