Religious marriage is everything.
Personally, I love the civil benefits I am entitled to of filing a joint tax return, getting a surviving spouse estate tax exemption, and receiving social security spousal benefits.
(BTW, I was married in a church to my dear husband 39 years ago this month. I'm not discounting the religious side of marriage. However, as a practical matter, the civil side of marriage is important in today's world.)
If the laws of God are so unimportant to someone that they're secondary to the laws of man, I have to doubt the sincerity of that person's religious beliefs.
Personally, if I were a Christian minister I would reluctantly break man's unbiblical law and go to prison rather than to obey an unbiblical law enacted by a liberal anti-Christian judge, justice, or court simply by judicial fiat. The bible commands us to obey government's laws whether or not we agree with them, but not if the law in question is itself in violation of God's higher law, as were Roman laws against the propagation of Christianity.