What is the Prerogative Writ of Prohibition

Prohibition is a royal prerogative writ involving a petition made to the sovereign, in Canada in the form of her Superior Court Justices, to stop a lower court or government official from doing something. Because it only prevents future action, and doesn't cancel decisions that have already been made, it's often used in combination with the other writ of certiorari which will vacate the earlier decision prior to prohibition stopping future similar decisions. 

Why Apply for Prohibition

If you don't like something a lower court or government official is doing, you can stop it by having a writ of prohibition issued. It is sort of the criminal law equivalent of the injunction. 

How to Seek Prohibition

Only a court of "original inherent jurisdiction" has authority under the common law to grant the writ of prohibition. So you need to proceed to a superior court, which in Ontario is the Superior Court of Justice. 

Prohibition is sought by way of notice of application and supporting affidavit with exhibits, explaining what kind of lower court or official conduct you objection to, and the basis for the objection. 

It's possible to appeal a prohibition decision by a Superior Court up to the Court of Appeal.