1) God only considers a couple married when they are legally married. The scriptural support typically given to this view is the verses that advocate submission to the government (
Romans 13:1-7;
1 Peter 2:17). The argument is that if the government requires certain “paperwork” to be completed before a marriage is recognized, a couple should submit themselves to whatever process the government requires. It is definitely biblical for a couple to submit to the government as long as the requirements do not contradict God’s Word and are reasonable.
Romans 13:1-2tells us, “Everyone must submit himself to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God. Consequently, he who rebels against the authority is rebelling against what God has instituted, and those who do so will bring judgment on themselves.”
Read more:
http://www.gotquestions.org/marriage-constitutes.html#ixzz3OqvykqXn