The leading ship in a fleet is known as the flagship. It is typically the largest, most well-armed ship in the fleet. It is called a flagship because it flies a flag indicating the presence of the fleet commander on board.
For 1500 years God had a definite two-track arrangement among the nations. There was Israel and the rest of the nations (Amos 3:2). Israel was the flagship of the fleet of nations. Yahweh had called them into special relationship with Him that they might be a blessing to the rest of the world (Genesis 12:1-3).
But something happened to Israel somewhere along the way. They fell out of love with their mission and in love with their status as a flagship nation. They began to view themselves not as the elect chosen by God to be a blessing, but as the elite who were a cut above everyone else.
It’s in this context that Paul says in Romans 3:20, “Therefore no one will be declared righteous in God’s sight by the works of the law.” I suppose it’s natural to look at the phrase, “the works of the law” and want to understand it as referring to any/all of the Torah so that Paul is saying something like the Jews won’t be saved by law keeping. That would certainly be true in the meritorious sense but is that the sense in which Paul is speaking here? It seems unlikely—especially in light of the fact that he has just finished speaking about works in a different (instrumental) sense and how at the judgment it will be those who have done good and obeyed the law who will be saved (Romans 2:6-16, esp. v. 13). Salvation is a gift that must be received by faith but a saving faith is one that does good and obeys and Paul clearly doesn’t think his speech is in any way “ungracious” so neither should we.
But immediately after his section on judgment (2:17-24), he begins to discuss circumcision. In fact, it is mentioned half a dozen times between 2:25 and 3:1. This is not by accident. Circumcision was a mark of distinction—perhaps the most prominent aspect of Jewish national identity/status. The problem Paul deals with in Galatian and Romans is not legalism—Jewish Christians wanting to “earn” salvation, but nationalism—the idea that being right with God involved bearing the identifying marks of Israel (circumcision, dietary laws, the Sabbath, etc.). As one writer noted, it wasn’t a matter of grace but race. They pursued a national righteous instead of the righteousness that came through Christ (Romans 10:1-4).
In this context, “works of law” refers to circumcision and other distinctive aspects that gave the Jewish people their national identity. Since we’re in a section where Paul is stressing oneness (i.e., how everyone is under sin and everyone is saved through faith in Jesus), he is crushing the idea of the need for national identity. As he will tell the Galatians, “So in Christ Jesus you are all children of God through faith, for all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Jew nor Gentile, neither slave nor free, nor is there male or female, for you are all one in Christ” (Galatians 3:26-28). Many of the Jews understood oneness as meaning everyone had to become like the flagship but Paul makes it clear that oneness comes through being in and like Christ.