Ecclesia de Eucharistia §45

⁴⁵ While it is never legitimate to concelebrate in the absence of full communion, the same is not true with respect to the administration of the Eucharist under special circumstances, to individual persons belonging to Churches or Ecclesial Communities not in full communion with the Catholic Church. In this case, in fact, the intention is to meet a grave spiritual need for the eternal salvation of an individual believer, not to bring about an intercommunion which remains impossible until the visible bonds of ecclesial communion are fully re-established. This was the approach taken by the Second Vatican Council when it gave guidelines for responding to Eastern Christians separated in good faith from the Catholic Church, who spontaneously ask to receive the Eucharist from a Catholic minister and are properly disposed. This approach was then ratified by both Codes, which also consider – with necessary modifications – the case of other non-Eastern Christians who are not in full communion with the Catholic Church.