Since 1790 the United States government has defined and recognized marriage for it’s military personnel, that was unconstitutional? They didn’t seem to know that.
We have every flavor of church in America, polygamy churches and gay marriage churches and everything else, that means that there is no defined marriage, and as far as your forbidding atheists to marry, are you going to require a God oath for a sergeant to get married?, What if he is gay, or Muslim and wants lots of wives?
Well-then I guess the Christian church needs to get its shit in a sock and start acting like it’s something different (i.e. acting like marriage is a permanent lifetime commitment, rather than allowing/accepting divorce/remarriage for every little thing), no?