Christ is in our midst!!
An interesting note, I read of an Orthodox priest in Michigan recently, who stated he will no longer perform legal marriages. He will perform sacramental marriages in church and the couple will have to get the state to perform a civil ceremony for legal purposes. That was his way of avoiding the whole same sex thing.
I've heard that this is done in some European countries and was the way to go in the former Soviet Union where the state did not recognize the Church to do any legal marriages. I've suggested this to clergy of every stripe and they look at me like I have two heads. By refusing to be an official of the state in witnessing and recording marriages, clergy would be outside the reach and challenge of this same sex marriage issue.
Some of the people who want to challenge churches will do so just to make a legal case. Look at the people who focused on the Colorado cake maker. There were plenty of other cake makers who would comply with the same sex marriage cake, but the people who went after him singled him out for persecution.
IMHO, the best way to go about this is to bless marriages of regular church people and let those who come as irregular or simply strangers wait a length of time to see if they are really committed members. Meanwhile they can go to the Justice of the Peace, a mayor or other government official legally permitted to witness marriage, a Notary Public, or--as in some states now--to anyone who obtains the necessary credential to witness and record marriages.
Fourteen years ago, I attended the marriage of a family member in California. The officiant was a friend who had obtained a license to witness and record their marriage. He had paid a fee and had the authority to witness just that marriage. He had three business days to go to the county courthouse and record the marriage certificate with the signatures of his own and the two official witnesses. That's permitted by law in that state.
My advice to clergy will continue to be--think outside the box and avoid an expensive legal challenge to witnessing marriages.