The LCMS takes heat from other evangelicals because of its practice of close[d] communion. Close[d] communion means that a common confessional affirmation is required in order to celebrate the Supper together. In LCMS churches, the requirement is that communicants at least confess the doctrine as they've learned it in the Small Catechism, and particularly affirm the real presence. Practices vary among LCMS congregations how the table is fenced.
I don’t fret about close communion a whole lot. I think the LCMS position is a position implied by the nature of the Supper itself, as it creates and expresses our unity with Christ both vertically and horizontally. Lots of evangelicals disagree.
Internet Monk (IM) recently posted an extended entry criticizing practices that are typical at many (although not all) LCMS churches (http://www.internetmonk.com/archive/jesus-the-paperwork).
Here are some random observations.
Almost every person I know who objects to close[d] communion attends a church that in fact practices close[d] communion, even though they say their church practices open communion.
For example, IM observes the practice of what he styles “open" communion includes the following:
“Baptized believers (Apostle’s/Nicene level) are invited to participate, but if you are a guest, it’s an honor system. Since you are a guest, no one is going to ask you 20 questions. We’re all guests of Jesus at his table.”
There are two aspects of close communion. First, does your church require anything of those who come to the table for the Supper? Secondly, what level of review does your church provide to those who say they meet those requirements?
On the first level, IM manifestly endorses doctrinal requirements that must be satisfied prior to receiving the Supper – you must be baptized and you must agree with the Nicene creed.
I gather that IM nonetheless says that this is “open communion” because, even though only “believers (Apostle’s/Nicene level) are invited to participate,” whether you do so is a matter of your own judgment. “Since you are a guest, no one is going to ask you 20 questions. We’re all guests of Jesus at his table.”
So here are some observations:
 Where, exactly, is the rub? Is it having doctrinal requirements, or is it the honor system?
If an LCMS church simply said, “All who agree with Augsburg are welcomed at the table,” and simply accepted that those who approached the altar agreed with the Augsburg, would he think that that is open communion? (To my knowledge, many LCMS churches fence the table only verbally, and serve anyone who comes forward.)
On the other hand, if a Baptist church required only affirmation of Nicaea, but insisted that you touch bases with the pastor or a deacon (or elder) prior to the service in order expressly to affirm that belief, would he reject that as too close to “20 questions”?
So it’s unclear, at least to me, whether IM’s problem with the LCMS is with having a confessional affirmation – any confessional affirmation – or whether it’s that he thinks that the LCMS has the wrong confessional affirmation, or whether it’s that the LCMS doesn’t use the “honor” system to determine whether someone agrees with the confessional affirmation necessary to commune at the table.
 Why draw the line at Nicaea? Why not Chalcedon? Why not Constantinople II? Why not “salvation through grace alone by faith alone,” the confession on which the faith depends, but is not a topic of dispute covered by Nicaea?
Or even, why not less than Nicaea? Why not accept a simple affirmation that “Jesus is lord,” and allow non-Nicaeans to commune? On what argument does IM (and others) say “this far is necessary, but no further”?
 “Since you are a guest, no one is going to ask you 20 questions. We’re all guests of Jesus at his table.”
We’re all guests of Jesus at his table, sure enough. It’s unclear why this mean that churches should rely only on the "honor system" and should not ask unknown communicants whether they believe in Jesus or even whether they've been baptized.
, for example, would seem to draw precisely the opposite conclusion from IM's premise that "it's Jesus' table."
“[L]et no one eat or drink of your Eucharist except those who have been baptized into the name of the Lord, for the Lord has also spoken concerning this: ‘Do not give what is holy to dogs’” (9.5).
We’re all guests at Jesus' table because we belong to Jesus. Why is asking a visitor whether he belongs to Jesus and, hence, whether he belongs at Jesus’ table, so terrible? On what basis is it worse to ask “20 questions” of a visitor than it is to serve the Body and Blood of Jesus to one to whom it does not belong?
I appreciate that IM’s conscience tells him one thing, but why could not another agree with the perspective of the Didache
, concluding that the risk of profaning the Body and Blood of Jesus is worth asking a question or two and not relying solely on the “honor system”?
So what conclusions?
First, IM seems to me to endorse a system of close communion. He would restrict access to the table to “baptized believers” who affirm Nicaea. So IM is quite willing to engage in line drawing. It just happens that he prefers where he and his churches draw the line rather than where LCMS churches draw the line. That's fine, but I have yet to see an argument as to why his version of close communion is in any way more biblical than “my” version of close communion.
Further, how does he answer his own argument for inclusion? “We’re all guests of Jesus at his table,” right? So why not include Arians, JW’s, Mormons or others? Why not make it a truly open table to anyone who can affirm that he “believes” in Jesus? On his own terms, how would IM justify excluding non-Nicaean believers from Jesus' table? We're all guests at the table, after all. On his own terms, what right does IM have to exclude anyone?
Finally, if the table is for “baptized believers” only, then what’s wrong with asking someone whether they’ve been baptized, whether they believe in Nicaea (or whatever)? Biblically speaking, why must we rely on the honor system? I'm not necessarily opposed to fencing the table verbally, I just don't see where the Bible limits a church solely to the "honor" system.