Fiat

1. An arbitrary or authoritative command or order to do something; an effectual decree.

   A presidential fiat.

2. Authorization, permission or (official) sanction.

   A government fiat.

3. (English law) A warrant of a judge for certain processes.
4. (English law) An authority for certain proceedings given by the Lord Chancellor's signature.

verb

(used in academic debate and role-playing games) To make (something) happen.