Council of Trent: Session VII, Reformation, Chapter VI

CHAPTER VI. What unions of Benefices shall be accounted valid.

Unions in perpetuity, made within forty years, may be examined into by the Ordinaries, as delegated by the Apostolic See, and such as shall have been obtained by surreption or obreption shall be declared null. Now those are to be presumed to have been surreptitiously obtained, which having been granted within the aforenamed period, have not as yet been carried into effect wholly, or in part, as also those which shall henceforth be made at the instance of any person soever, unless it shall be certain that they have been made for lawful, or otherwise reasonable causes, which are to be verified before the Ordinary of the place, those persons being summoned whose interests are concerned: and therefore (such unions) shall be altogether of no force, unless the Apostolic See shall have declared otherwise.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).