I think a bishop can marry people and so can missionaries. Basically, anyone with an ecclesiastical endorsement can perform marriages.....and you get that on the internet.
Not when I was a missionary in 83 - 85. We all carried a ministerial certificate and were told we could perform marriages.
Maybe they changed it. Legally, anyone can perform a "religious" marriage if the have a ministerial certificate, which anyone can get on line these days. I've performed many marriages with mine :)
Some states (Ohio for one) require a "license" to marry people (or at least they did) for the marriage to be considered 'valid' which is of course VERY old-fashioned....
OK, so they send a mish home, but what about a non-mish;? are they going to discipline someone for performing a wedding? I hardly think so!!!
They asked if DH, former Mo, could perform their marriage ceremony. He immediately became a member of some Universal Church in their state and ended up performing their ceremony, and two other marriages for the relatives-in-law. Everybody was happy because he consulted with each couple about what they wanted him to say. There were some mixed marriages here, i.e. religiously mixed and everyone was happy.
DH even learned some Polish words to say at the first ceremony. The family loved it! They later said they knew what he was trying to say.