§1. The college of bishops exercises power over the universal Church in a solemn manner in an ecumenical council.
§2. It exercises the same power through the united action of the bishops dispersed in the world, which the Roman Pontiff has publicly declared or freely accepted as such so that it becomes a true collegial act.
§3. It is for the Roman Pontiff, according to the needs of the Church, to select and promote the ways by which the college of bishops is to exercise its function collegially regarding the universal Church.
Source: Code of Canon Law (Vatican.va)