Well as God does not do paperwork, no paper or law is neccesary to marry two people. This is what I think...
No paper has ever made two people commit. No law has ever made two people commit to eachother. Love commits. It is the LOVE between two people that make them bond and become ONE! Yes I agree if the law of the land says you should LEGALLY be married, then do so. But that NEVEr detered millions to divorce after.
When the "Voortrekkers" or the frontier people moved inland to the wild, there were no laws there. They only had their faith and their Bibles. So when two young people will fall in love and they wanted to get married, the group leader, would bless them and they were considered married.
What is marriage. Marriage is the COMMITMENT between two people that wants to live together in love. I think the moment two people commit to eachother, they are married in God's eyes. Why would two people want to live togather in the first place. Only one of two reasons... fleshly lust, or heavenly match. One will work the other not, if God does not change it.
I married out of pride and stupidity, cheated many times despite the whole church seromony and legal papers. But then God stepped in and helped me to be a husband as I should be. Then there is two of our friends, they NEVER went through the church thing or the legal thing, but they are living together and NEVER cheated on one-another. They are the strongest in the commitment of ALL I know. Who is the more or better married in God's eyes?
In afrikaans we say two people "TROU". Trou in afrikaans means , commit, honor, bond, or join. It is like a life long promise to be TRUE to eachother. That promise can be hnored by God if neither lies about the commitment. But that commitment can be shared in the privacy of a room between two people. Even if they are unbelievers, the promise and commitment can be honored. And the moment they share a bed, it is irreversable. If they then break the commitment it is adultery. But if they do not, they will be married in God's eyes and He can bless them as any other married in God couple!