Premarital sex is a sin according to the Bible (1 Corinthians 7:9; Hebrews 13:4). I wonder how queer theology churches such as the Evangelical Lutheran Church in America (ELCA) understand this topic. Do they believe extramarital sex is a sin?
My understanding of the ELCA branch of the Lutheran church, is that the morality of sexual intimacy being restricted to the rite of marriage is de facto an open question. That is, if it feels good do it, as long as it is by mutual consent. For example, see this site.
Also, Nadia Bolz-Weber was installed on August 20 as the first pastor of public witness in the Evangelical Lutheran Church in America. She was called to the role of pastor of public witness by the ELCA’s Rocky Mountain Synod and remains a leader in good standing. In her interviews she has gone on public record as saying the following about being divorced:
...I get divorced, like the most amicable divorce you can imagine. No lawyers, no acrimony. It was great, right, it was like actually really lovely. But I get together with my boyfriend and start having sex and...it felt like an exfoliation of my whole spirit. I'm like 'This is so good for my brain chemistry, and my body, and my heart. And I’m like...why in the world would the Church say ‘Don’t do this?’ Like I could tell it was what I needed, and it was so good. And then 10 days later, after we get together...I have to go to Europe for 3 1/2 weeks on a book tour, because the U.K and the German edition of my book came out...3 ½ weeks after years of sexlessness and 10 days of having sex, right, my mind was like swirling, I was like ‘What...is happening?!’ (Sourced from here.)
In respect to the two passages mentioned, I suspect they would view those as cultural accommodations with the abiding principle that sexual intimacy is fine if done with mutual consent. They might appeal to 1 Corinthians 7:36 which seems to allow sex with whoever is past the bloom of youth, but with the encouragement of marriage being an added exhortation:
If anyone thinks he is acting inappropriately toward his virgin, if she is past the bloom of youth and it seems necessary, he should do what he wishes; he does not sin. Let them marry...