§1. The decrees of an ecumenical council do not have obligatory force unless they have been approved by the Roman Pontiff together with the council fathers, confirmed by him, and promulgated at his order.
§2. To have obligatory force, decrees which the college of bishops issues when it places a truly collegial action in another way initiated or freely accepted by the Roman Pontiff need the same confirmation and promulgation.
Source: Code of Canon Law (Vatican.va)