Could this be a NT validation of the Law?
Romans 4:15 and 5:13 tells us what sin is for everyone. Romans 14:23 and James 4:17 tell us what sin is for the individual, which is conscience based. When the New Testament speaks of immoralities, by definition that word means something that is contrary to the Law of God. The only way several of the issues can be resolved is by looking at the difference in classes. Everyone is under the Law because that determines what sin is. The wages of sin is death. Sin is imputed when one violates the Law. The Law specifically states that it can't be changed (Deuteronomy 4:2 and 12:32).
However, there's the law of the bondservant, which applies to Christians who were bought with a price. Becoming a Christian means entering the household of Christ, who is the undisputed Master. He has the authority to set his own rules for His people, so if He doesn't want the men having sex with prostitutes (1st Corinthians 6:15-16) and if He doesn't want His married bondservants to divorce for any reason (1st Corinthians 7:10-11) or marrying someone other than one of His bondservants (2nd Corinthians 6:14) then He has the right to make those rules. Romans 14 with respect to keeping the sabbath and eating meat sacrificed to idols is another example.
Take the issue of divorce. Certainly a contentious issue. Genesis 2:24 did not give the man the authority to end a marriage just like it didn't restrict him to taking more than one wife. As Christ said in Matthew 19, "
Moses permitted you to divorce your wives, but from the beginning it has not been this way." From the beginning? Genesis 2:24, no authority given to divorce her. So, Moses permitted it and that became part of the Law and that can't be changed, so any man under the Law (not a Christian) has the authority to divorce his wife for adultery (porneia). However, in 1st Corinthians the regulation was specifically given to the married bondservants of Christ, by Christ, that they are not to divorce and no exceptions were given. What you'd call the "House Rules" of being a Christian. Paul then gave the instruction to those unequally yoked. The point is that when looked at from the standpoint of the change in status between the person under the Law and the person in Christ, it makes perfect sense as it reads.
However, the whole monogamy thing created the pressure to divorce. God created a perfect plan, Moses fiddled with it, Christ set it back the way it was for His bondservants and then the church came along and threw it all out for a mix-mash of pagan beliefs, stoic philosophy and Roman law. Phooie.
This also explains not being under the Law. It isn't that the Law no longer applies, it means that in Christ there is specific instruction for those in His house. As Christ said, not the slightest stoke or shading of the pen of what is written in the Law shall pass away until all things are complete, but for Christians it's different because they are in a different category. Their life is not their own, they were bought with a price and they have a master. Which is why believing in your heart and confessing with your mouth that Jesus Christ is Lord means you're saved. What does that "Jesus Christ is Lord" mean? That He is your Master. Your Lord. When you apply that to modern church doctrine suddenly people start screaming, because of all the centuries of interpretations by people who wanted to have their cake and eat it too.