I’d refer them to the priest, kindly explaining that if they aren’t in communion with the church, they shouldn’t receive.
Also, not to be snooty or anything, but I just want to point out that the actual name of your role is “Extraordinary Minister of Holy Communion.” A “Eucharistic Minister” is a priest or bishop (not even a deacon), because they can confect the Eucharist. You only help with holy communion, hence the name. I only point this out because the church has asked us to be careful with these terms. Good day to ya!
Redemptonis Sacramentum:
[154.] As has already been recalled, “the only minister who can confect the Sacrament of the Eucharist in persona Christi is a validly ordained Priest”. Hence the name “minister of the Eucharist” [Eucharistic minister] belongs properly to the Priest alone.
…]
[156.] This function is to be understood strictly according to the name by which it is known, that is to say, that of extraordinary minister of Holy Communion, and not “special minister of Holy Communion” nor “extraordinary minister of the Eucharist” nor “special minister of the Eucharist”, by which names the meaning of this function is unnecessarily and improperly broadened.
Hope this helps.