The College of Cardinals, formerly styled Sacred College of Cardinals, is the body of all cardinals of the Catholic Church.
A function of the college is to advise the pope about church matters when he summons them to an ordinary consistory, a term derived from the Roman Emperor's crown council. It also attends various functions as a matter of protocol, for example, during the canonization process.
It also convenes on the death or resignation of a pope as a papal conclave to elect a successor, but is then restricted to eligible Cardinals under the age limit, which was set for the first time in 1970 by Pope Paul VI at 80.
The college has no ruling power except during the sede vacante (papal vacancy) period, and even then its powers are extremely limited by the terms of the current law, which is laid down in the Apostolic constitution Universi Dominici gregis (1996) and the Fundamental Law of Vatican City State.
Historically, cardinals were the clergy serving parishes of the city of Rome under its bishop, the pope. The College acquired particular importance following the crowning of Henry IV as King of Germany and Holy Roman Emperor at the age of six, after the unexpected death of Henry III in 1056. Until then, the Holy See was often bitterly fought for among Rome's aristocratic families and external secular authorities had significant influence over who was to be appointed pope, and the Holy Roman Emperor in particular had the special power to appoint him. This was significant as the aims and views of the Holy Roman Emperor and the Church did not always coincide. Churchmen involved in what has become known as the Gregorian Reform took advantage of the new king's lack of power and in 1059 reserved the election of the pope to the clergy of the Church in Rome. This was part of a larger power struggle, which became known as the Investiture Controversy, as the Church and the Emperor each attempted to gain more control over the appointment of bishops, and in doing so wield more influence in the lands and governments they were appointed to. Reserving to the cardinals the election of the pope represented a significant shift in the balance of power in the Early Medieval world. From the beginning of the 12th century, the College of Cardinals started to meet as such, when the cardinal bishops, cardinal priests and cardinal deacons ceased acting as separate groups.