I would give ANYTHING to see a priest publicly refuse to give the Eucharist to one of them. I'm not sure if there is an actual procedure for this, but I suspect there is.
We have a very close friend, a young traditional priest from Italy. I have seen him deny communion for cause. It is over in a flash, hardly noticeable to anyone not alerted by the reddened face of the recipient who was passed by. The person knows, the priest and server know, and few others as after all their minds would be absorbed in the event, not in watching the others.
In the Tradition, it is only the priest who distributes and he puts it on their tongue, not in their hands, and moves at a rhythm that passes them by so quickly it is hard to spot.