This must be a catholic thing.
My brother-in-law had Life Teen masses on Sunday evenings, and many of the Catholic kids brought their non-Catholic friends with them. Their non-Catholic friends wanted to be a greater part of the Mass, but couldn't receive Holy Communion, so my b-i-l simply told them to come forward, and if he saw that their arms were crossed, he'd give them a Blessing, instead of the Body and Blood of Christ. He knew who was Catholic, and who was not, because he was closely involved with the Catholic high school, and the youth program in the Parish.