Fiat and Papal bull

Fiat noun - An order publicly issued by an authority.

Papal bull and fiat are semantically related. In some cases you can replace phrase "Papal bull" with "Fiat", this terms are similar.

Papal bull noun - A formal proclamation issued by the pope (usually written in antiquated characters and sealed with a leaden bulla).

Fiat and papal bull are semantically related. You can use "Fiat" instead a noun phrase "Papal bull".