Can Only Confessing Members Participate in the Lord's Supper?

Thanks, Art, for this question.  The CRC has no required pattern for inviting visitors to participate in the Lord's Supper but leaves the oversight of the sacrament to the elders of the local church "in a manner conducive to building up the body of Christ and in keeping with the teachings of God's Word" (Church Order Article 60).  In his Church Order Commentary on that article, Dr. Henry DeMoor lists half a dozen different ways that he had experienced the supervision of the Lord's table in CRC congregations, ranging from a pre-service conversation with guests to no announcement at all.  

From a theological standpoint, we believe that the Lord's Supper is for those who trust that their sins are covered by the death of Christ, not for unbelievers (see Heidelberg Catechism Q&A 81-82). Thus many CRCs have utilized some kind of public announcement that makes this understanding clear; in many cases, though, the elders then leave it to the conscience of any visitors whether or not to celebrate communion.  

Many CRC congregations today do not require baptized children to make profession of faith prior to being welcomed to the Lord's Supper, so it should not be assumed that all who participate in the sacrament are professing members.  However, these baptized members are still expected to participate "under the supervision of the elders" (Church Order Article 59-a).

For more information on the CRC's understanding of the Lord's Supper, you might also check out the links at this page.