IANAL, but I was a real Christian minister for a while (3+ years, actually). I was never officially ordained, however. Ordination in my denomination means that the elders of your home church deem you “worthy” and pass their blessing, and then you get a certificate or something. In my case, however, the good people of Rochester Christian Church in Rochester, Illinois didn’t “think the time was right,” or something. I didn’t pursue the matter, since I already had a preaching gig at the time and the church I was preaching at never made an issue of it (actually, they never asked).
Apart from preaching, calling, visiting the sick, etc., I did about 10 baptisms, three funerals and three weddings. The baptisms and funerals presented no real legal issues, of course. Now, on to the weddings.
All three weddings I did were in Illinois. On the marriage license I signed my name followed by the words “Minister of Christ.” No one has asked me or any of the people I married about it, and since the parties involved all paid the fee and filed the license like they were supposed to, who the hell cares?
Another note: when Mrs. Rastahomie and I got our marriage license in Jasper County, Missouri, I asked the clerk if the minister doing the wedding would need to present some sort of credentials. She told me that since we had shown our I.D. and paid our fifty bucks, the good people of Jasper County could care less if Joe the Town Drunk did the ceremony, so long as he signed the form and mailed it back.
Bottom line: check with your county clerk. I imagine 99% of the county clerks in America want only your ID, your money, and someone else’s signature on the license. YMMV