Long before the early twentieth century, leaders in the Stone-Campbell Restoration Movement more or less agreed on two points related to the question, who may partake of the Lord's Supper? First, the Supper was for Christians. Second, it was no one's place to identify and prevent someone from eating the Lord's Supper. Again, nineteenth century thought leaders were the ones who had established these two principles. The two following quotes from an early twentieth century source indicate its standing among the Churches of Christ at that time:
“The table of the Lord is for those in his kingdom, for those who cherish him in their hearts and who believe in his sacrificial death. Others should not presume to eat.”
Because each person should “examine himself” (1 Cor. 11:28), no “man or set of men has the right to sit in judgment and determine who shall and shall not eat the supper. The Lord has not conferred police powers on any one to stand guard over his table” and turn away “those who may be judged as unworthy.”
Source
C.R. Nichol and R.L. Whiteside, Sound Doctrine, 6th ed. (Clifton, TX: Nichol Publishing Company, 1920), 1:167, 169.