The Ilvian Proclamation was a legal document made by the Bajoran Provisional Government after the end of the Cardassian Occupation of Bajor. It declared that every Bajoran who was a member of the Bajoran Occupational Government was sentenced to exile, and included a list of named individuals so exiled.
Secretary Kubus Oak was fourth on the list, and when he returned to Bajoran space in 2370, he was arrested aboard Deep Space 9. (DS9: "The Collaborator")
The Star Trek Encyclopedia (4th ed., vol. 1, p. 359) stated that the proclamation was apparently named after Star Trek: Deep Space Nine art director Randy McIlvain.
Presumably, the Ilvian Proclamation was issued from the city of Ilvia.
According to the script, the pronunciation for Ilvian was "ILL-vee-un".