Q - We were married by a pastor in his office as we are both over 75. One of us is Catholic the other Protestant. Can the Catholic still receive Communion?
A - Thanks for the question. If the pastor was Catholic, then the Catholic can most likely still receive Communion. If he was a non-Catholic pastor (and you didn't receive permission from the Catholic Bishop beforehand), then the marriage needs to be convalidated (sometimes called "recognized") by the Catholic Church before the Catholic spouse can receive the Eucharist. This is because the Catholic is still bound to marry according to the guidelines set forth by the Church. Until this happens, the marriage is not considered valid by the Church.
To have the marriage convalidated is a fairly simple process. You will need to meet with a priest or deacon, tell them your situation, fill out some paperwork, and then schedule a ceremony for the convalidation. It is usually a small, private ceremony. If one of you was divorced and the former spouse is still living, then the process of anullment (technically a declaration of nullity) must be done before the convalidation. This takes much more time and effort, but is necessary because the Church still recognizes the first marriage as valid, until death, unless the couple was never validly married int he first place.
The church views all marriages with the utmost respect and considers them sacred in the eyes of God. It is a bringing together of two people, until death of one of the spouses. This joining together is the beauty of the marriage. The ultimate purpose of the marriage is to help the spouses grow in holiness, get to heaven, glorify God and raise their children with the same goals. With this in mind, the rules of the church help us to achieve these goals by giving us guidelines for how to proceed properly. We shouldn't see them as impediments to doing as we wish, but rather as help to us in achieving higher goals.
Peace to you both.