If it counts for anything, the Roman Church allows Eastern Orthodox, Oriental Orthodox, the Assyrian Church of the East, and the Polish National Catholic Church to commune, but ALSO says those persons should respect the discipline of their own Churches. They will permit Anglicans, Lutherans, and Old Catholics to commune in extreme circumstances, such as near death issues, on a case-by-case basis. Missouri Synod technically allows only itself and the 35 or so Churches with whom we are in communion to commune. But some Pastors will permit believers in the Real Presence to commune, namely, any Lutheran, Anglican, OO, EO, RCC, Assyrian Church, Old Catholic, or Polish National Catholic. This is tolerated, as long as it is not advertised too loudly, due to the odd tension in our Church between top-down rule from St. Louis v. the odd congregational polity that has been a hallmark of our Church. That odd tension has always been, well, kind of messed up. Most Churches are either top-down, OR congregational, but I have never known one other than our own that is BOTH! Its a bit frustrating for me, coming from the Roman Catholic and Anglo-Catholic traditions, both of which are top-down traditions.