Universi Dominici gregis
Universi Dominici gregis is an apostolic constitution of the Catholic Church issued by Pope John Paul II on 22 February 1996. It superseded Pope Paul VI's 1975 apostolic constitution, Romano Pontifici eligendo, and all previous apostolic constitutions and orders on the subject of the election of the Roman Pontiff.
Universi Dominici gregis ("the Lord's whole flock", from the opening statement "The Shepherd of the Lord's whole flock is the Bishop of the Church of Rome, ..."), subtitled On the Vacancy of the Apostolic See and the Election of the Roman Pontiff, deals with the vacancy of the See of Rome, i.e., the papacy.
The constitution modified or in some cases confirmed the rules, for the conclave. It also clarified, during a sede vacante, which matters could be handled by the College of Cardinals and which matters were reserved for the future pope.