A reader writes:
I was recently asked to be a notary at my good friends wedding in a couple
of months.Immediately I thought I may not be able to do so because I am a practicing
catholic and this will be a non catholic wedding. Neither the bride or
groom are practicing catholics nor do they plan on getting married in any
type of church.
If neither of your friends has ever been Catholic then they are not bound by canon law to observe the Catholic form of marriage. They are therefore free to marry in any kind of service they want, religious or not.
Assuming that they have the capacity to marry (e.g., they are not presumably still married to someone else, despite a civil divorce), their marriage will be presumed valid.
Assuming that their marriage is presumably valid, there is no apparent canonical or moral reason why you could not serve as a notary, a deputy commissioner of marriages, or any similar role at their wedding. Canon law does not prevent Catholics, even lay Catholics, from officiating at such weddings, and as long as the marriage will be presumed valid, nothing in moral theology would do so either (assuming that there isn’t some other factor affecting the situation, like the vows expressly rejecting an essential property of marriage).
I’ve thought through this issue with some care, because I myself was asked to preside at the wedding of my sister (a never-before-married non-Catholic) to her fiance (another never-before-married non-Catholic), and after parsing the relevant factors and consulting with others, I ended up being deputized as a one-day deputy commissioner of marriages and peformed the ceremony.

