“If someone cannot talk or indicate by a sign that he believes, understands, and desires the sacrament–particularly if he has wilfully [sic] neglected it–we will not give it to him just anytime he asks for it. We have been commanded not to offer the holy sacrament to unbelievers but rather to believers who can state and confess their faith. Let the others alone in their unbelief; we are guiltless because we have not been slothful in preaching, teaching, exhortation, consolation, visitation, or anything else that pertains to our ministry and office.”

Luther, Martin. “Whether One May Flee From a Deadly Plague” (1527) Luther’s Works Vol. 43. Philadelphia: Fortress Press, 1969, page 135.

The Sacrament of Holy Communion both expresses and creates community. Practice today varies. Some err on the side of inclusion (that it creates community), some at the other end of the spectrum (that it expresses an already existing community).

Note that Luther doesn’t refer to church membership but to faith as the thing that admits one to the table of the Lord. I think that he would have to exercise godly pastoral judgement in doubtful cases. While being faithful in carrying out the many duties of his pastoral office.