It seems you may not be understanding that Paul used the term "LAW" in several different ways depending on the issues he was addressing. Among such different usages, the Law could pertain to the mosaic law (carnal/physical commands and ordinances) or to the entirety of the OT.
The Law of God (the whole Old Testament) has continuing relevance in this New Testament dispensation if it is used properly.
Paul wrote:
“We know that the law
is good, if a man use it lawfully” (1 Tim. 1:8). In other words, the Law of God (the Old Testament) has continuing relevance in this New Testament dispensation if it is used properly.
Paul’s statement in 2 Timothy 3:16-17 supports this claim. Writing under inspiration of the Holy Spirit long after the New Covenant was inaugurated, Paul asserts that the Old Testament is still profitable for doctrine, reproof, correction, and instruction in righteousness. This means there is a proper use of the Old Testament for Christians today.
I have previously presented at least 9 points demonstrating this continuing relevance.
The Law (the OT) very much "applies" to the NT generation.
In Romans 7:21-25, Paul said that he delighted in obeying the Mosaic Law and that he served it with his mind, but contrasted that with a law of sin that held him captive and that he served his flesh. This a summary of what he said previously, so Paul was contrasting God's Law with the law of sin, which means that we need to determine which of the two laws Paul was speaking about us not being under in this passage:
Romans 6:13-19 Do not present your members to sin as instruments for unrighteousness, but present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness. 14
For sin will have no dominion over you, since you are not under law but under grace. Slaves to Righteousness 15 What then? Are we to sin because we are not under law but under grace? By no means! 16 Do you not know that if you present yourselves to anyone as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness? 17 But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed, 18 and, having been set free from sin, have become slaves of righteousness. 19 I am speaking in human terms, because of your natural limitations. For just as you once presented your members as slaves to impurity and to lawlessness leading to more lawlessness, so now present your members as slaves to righteousness leading to sanctification.
The major clue is that verse 14 specifies that the law that we are not under is one where sin had dominion over us, which does not at all fit with Paul's description of God's holy, righteous, and good Law, but rather it fits perfectly with his description of the law of sin that was causing him not to do the good that he wanted to do. Furthermore, Romans 3:20 says that the Mosaic Law was given to reveal what sin is, Romans 7:7 says that the Law is not sin, but that it reveals to us what sin is, and Romans 7:12 says that the Law is holy, righteous, and good, so in regard to Romans 6:13, it is the Mosaic Law that instructs us how to avoid presenting our members to sin as instruments for unrighteousness and how to present our members to God as instruments for righteousness. In Romans 6:15, it says that being under grace doesn't mean that we are permitted to sin, which again means that we are not permitted to transgress what God revealed to be sin. In Romans 6:16, we are to present ourselves to God as obedient slaves, which again involves submitting to His Law. In Romans 6:19, we are again told not present our members as slaves to impurity and to Lawlessness, but to present ourselves as slaves of righteousness leading to sanctification, and the Law is God's instructions for how to do this. So neither Romans 6:14 itself nor the surrounding verses indicate that we are not under God's Law, but just the opposite. In Psalms 119:29, David asked God to be gracious to him by teaching him to obey His Law, so it is a fundamental misunderstand of God's grace to think that it is opposed to His Law, as though a house divided against itself could stand, but rather God is gracious to us by teaching us how to rightly live in accordance with His commands.
Paul also said in Romans 7:14 that the Mosaic Law is spiritual and in Romans 8:7 that those who have a carnal mind refuse to submit to the Mosaic Law, so it is a mistake it is a fundamental mistake to refer to the righteous works that it instructs as being carnal. In Galatians 5:19-23, everything listed as being carnal works that are against the Spirit are also things that are against what the Mosaic Law instructs, while everything listed as fruits of the Spirit are in accordance with what the Law instructs, so it wouldn't make any sense to interpret Galatians 5:18 as referring to us as not being under the Mosaic Law if we are led by the Spirit, especially considering that the Spirit has the role of leading us to obey the Mosaic Law (Ezekiel 36:26-27). Rather, it is again the law of sin that Paul served with his flesh that stirs up the works of the flesh that are against the Spirit.
We are not "under" the law in the sense that the righteous works (and carnal ordinances) of the Law cannot provide us with the life of Christ. Only the person of Christ can do that through faith. Through the person and work of Christ the universal principles/truths contained in the body of OT commands can be fulfilled in us and in our lives.
So we are not under the law pertaining to the means of justification.
The one and only way to become justified that there has been is by faith, so it has always been a fundamental misunderstanding of God's Law to think that it was ever given to provide the means of justification. According to Matthew 11:28-30 and Jeremiah 6:16-19 that Law is intended to be the good way where we will find rest for our souls, but if someone perverts the Law by trying to become justified by obeying it, then they rob it of the rest that it was intended to give. In Matthew 23:23, Jesus said that faith is one of the weightier matters of the Mosaic Law, and obedience to it is straightforwardly about having faith in God to guide us in how to rightly live, so we are justified by faith and by the same faith we are required to be careful to live in obedience to all of God's commands.
According to Deuteronomy 30:15-20, the Law brings life and a blessing for obedience, according to Proverbs 3:18, that Law is a tree of life for all who take hold of her, according the Matthew 19:17 Jesus said that if we want to enter life, then obey the Law, and according to Galatians 3:21, if a law had been given that could give life, then righteousness would indeed be by the Law, so can the Law bring life or not? As Jesus stated, faith is one of the weightier matters of the Law, so faith has always been a key component, without which keeping the Law does not impart life.
