What exactly is the "Law" mentioned in Galatians?

Galatians 2:11-14 NLT

But when Peter came to Antioch, I had to oppose him to his face, for what he did was very wrong. When he first arrived, he ate with the Gentile believers, who were not circumcised. But afterward, when some friends of James came, Peter wouldn’t eat with the Gentiles anymore. He was afraid of criticism from these people who insisted on the necessity of circumcision. As a result, other Jewish believers followed Peter’s hypocrisy, and even Barnabas was led astray by their hypocrisy. When I saw that they were not following the truth of the gospel message, I said to Peter in front of all the others, “Since you, a Jew by birth, have discarded the Jewish laws and are living like a Gentile, why are you now trying to make these Gentiles follow the Jewish traditions?

A very critical point to note when understanding the book of Galatians. Paul describes how Peter forsakes his liberty by refusing to eat with the Gentiles when some of their Jewish friends arrives. For the fear of Criticism, Peter demonstrated a lack of conviction in Justification by faith in Christ. Fear of what? Jewish Traditions of eating only with the Circumcised (the issue is not with the 10 Commandments, i.e Murder, Theft, Adultry, etc.). On this basis, he continued,

Galatians 2:17-21 NLT

But suppose we seek to be made right with God through faith in Christ and then we are found guilty because we have abandoned the law. Would that mean Christ has led us into sin? Absolutely not! Rather, I am a sinner if I rebuild the old system of law I already tore down. For when I tried to keep the law, it condemned me. So I died to the law—I stopped trying to meet all its requirements—so that I might live for God. My old self has been crucified with Christ. It is no longer I who live, but Christ lives in me. So I live in this earthly body by trusting in the Son of God, who loved me and gave himself for me. I do not treat the grace of God as meaningless. For if keeping the law could make us right with God, then there was no need for Christ to die.

This is consistent with the issue he is trying to address with the Galatian Christians; False teachers who are trying to introduce Jewish Traditions as part of the process besides Justification of Faith by Christ Jesus.

Galatians 2:4, 11-13 NLT

Even that question came up only because of some so-called believers there—false ones, really —who were secretly brought in. They sneaked in to spy on us and take away the freedom we have in Christ Jesus. They wanted to enslave us and force us to follow their Jewish regulations. But when Peter came to Antioch, I had to oppose him to his face, for what he did was very wrong. When he first arrived, he ate with the Gentile believers, who were not circumcised. But afterward, when some friends of James came, Peter wouldn’t eat with the Gentiles anymore. He was afraid of criticism from these people who insisted on the necessity of circumcision. As a result, other Jewish believers followed Peter’s hypocrisy, and even Barnabas was led astray by their hypocrisy.

And on this basis, he begin to address the Galatians on the falling back into Jewish Traditions (Not 10 Commandments). We can then understand the rest of Galatians with this foundation understanding.

Galatians 3:1-4 NLT

Oh, foolish Galatians! Who has cast an evil spell on you? For the meaning of Jesus Christ’s death was made as clear to you as if you had seen a picture of his death on the cross. Let me ask you this one question: Did you receive the Holy Spirit by obeying the law of Moses? Of course not! You received the Spirit because you believed the message you heard about Christ. How foolish can you be? After starting your new lives in the Spirit, why are you now trying to become perfect by your own human effort? Have you experienced so much for nothing? Surely it was not in vain, was it?