Can. 358

A cardinal to whom the Roman Pontiff entrusts the function of representing him in some solemn celebration or among some group of persons as a legates a latere, that is, as his alter ego, as well as one to whom the Roman Pontiff entrusts the fulfillment of a certain pastoral function as his special envoy (missus specialis) has competence only over those things which the Roman Pontiff commits to him.