I suppose this question is a little more complex than first expected.
This is a real situation that happened to me today. The EMHC asked me to come along with her to visit the people who she regularly visits. I don’t do this kind of ministry often, but I’d like to be involved with it. However, I suspect she was late for (or missed) Mass, and did not receive communion then. Neither did she get the Sacrament from the Priest as an extension of that Mass. After the Mass had ended, the church was empty she took the number of Hosts she’d need from the tabernacle (presumably with the Priests permission) and we took off. I felt a little funny about her just taking the Blessed Sacrament like that. But anyway, along the way she said something like “I didn’t receive today, so next stop I’ll take communion too”. Here I mentioned that I didn’t think she could do that. She said that she didn’t know that, and then didn’t try to later. She is the sweetest and kindest old woman in the church, not somebody who would consciously try to undermine the Church’s authority on such matters. But I wanted to find out where it was mentioned, so I could show her. I can’t seem to find it in the GIRM, but I suppose it’s got to be there somewhere.
Maybe that’s a clearer explanation. It should have been in connection with the Mass but wasn’t for whatever reason. I just wanted a reference. Anyone else know off hand?