In an e-mail entitled "Protestant Communion," a correspondent writes:
Hi there:
Simple question:
Should catholics receive communion in a non-catholic church?I am of the opinion that the answer is no. But, I’m having trouble finding
documentation to back me up. Would this be a violation of Canon law or
simply something that a more orthodox, observant Catholic ought to avoid.
Thanks for your time and your ministry,
There are a limited number of circumstances in which a Catholic can take Communion in a non-Catholic Church, but otherwise doing so is a violation of canon law. Unfortunately, the exceptions that exist presuppose that the sacrament is valid in the church were one is receiving Communion. This is the case in Eastern Orthodox churches and other Eastern churches (e.g., the Assyrian Church of the East), but it is not the case in Protestant churches, which is what I know you’re interested in.
The relevant canon is 844 (online here), but the whole canon is rather long, so I won’t walk you through all of it. Here’s the relevant part for your purposes:
ยง2. Whenever necessity requires it or true spiritual
advantage suggests it, and provided that danger of error or of indifferentism
is avoided, the Christian faithful for whom it is physically or morally
impossible to approach a Catholic minister are permitted to receive the
sacraments of penance, Eucharist, and anointing of the sick from non-Catholic ministers in whose Churches these
sacraments are valid.
Note the last bit in red. Unfortunately, Protestants did not retain valid holy orders and thus did not retain a valid Eucharist. Therefore, Catholics cannot receive this sacrament in Protestant churches.
Hope this helps!

