This is an interesting article which goes a long way in presenting Catholic teaching on reception of the Eucharist.
One month after Vatican and German delegates met in Rome to discuss a proposal put forward by German bishops to allow Protestant spouses in inter-denominational marriages to receive the Eucharist in certain circumstances, Pope Francis has rejected it.
In a letter dated May 25 and addressed to Cardinal Reinhard Marx, archbishop of Munich and president of the German bishops conference, Cardinal-elect Luis Ladaria SJ, the Vatican’s top authority on matters of doctrine, said the text of the German proposal “raises a series of problems of considerable importance.”
The letter was published June 4 on the blog of veteran Vatican journalist Sandro Magister.
The Holy See press office has confirmed the authenticity of the letter, which was also sent to members of the German delegation who attended a May 3 meeting between German prelates and Vatican official on the topic in Rome, including Cardinal Rainer Maria Woelki, archbishop of Cologne; Bishop Felix Genn of Münster; Bishop Karl-Heinz Wieseman of Speyer; Bishop Rudolf Voderholzer of Regensburg and Bishop Gerhard Feige of Magdeburg.
After speaking with Pope Francis about the matter in light of the May 3 discussion, Ladaria said the pope “came to the conclusion that the document is not mature enough to be published,” and cited three main reasons for the decision.
First, Ladaria stressed that admission to Communion of Protestant spouses in inter-confessional marriages “is a topic that touches the faith of the Church and has relevance for the universal Church.”
Allowing non-Catholics to receive the Eucharist, even in certain limited conditions, would also have an impact on ecumenical relations with other Churches and ecclesial communities “which should not be underestimated.”
Finally, he said the question of Communion is a matter of Church law, and cited canon 844 of the Code of Canon Law, which deals with access to the Sacraments of the Catholic Church.
Specifically, canon 844 states that “Catholic ministers administer the sacraments licitly to Catholic members of the Christian faithful alone, who likewise receive them licitly from Catholic ministers alone,” apart from a number of exceptions spelled out in the canon.
These exceptions include allowing non-Catholic Christians to receive the sacraments of Confession, the Eucharist, and the Anointing of the Sick by non-Catholic ministers in churches where these sacraments are valid “whenever necessity requires it or true spiritual advantage suggests it, and provided that danger of error or of indifferentism is avoided.”
More if you hit the link above.