If Jesus is the way for both Jew and Gentile in the 2nd Covenant, why wouldn't the Law be for all people in the 1st covenant? Everyone is a direct descendant of Noah.
I absolutely love this question! My friend, I have been scouring the Bible in a timeline, chronological order for years searching for this question (and many others, of course). I have only been studying the Story of God in this way for about five years, I believe, so my conclusions are still developing.
Thus far, I am able to determine that the answer lies within Chapters 1 and 3 of Ephesians, where Paul talks about the hidden, Eternal, Mysterious Plan of God, a Plan that has been in place since the beginning. Check this out . . . this is mind-boggling (as these words take us deep, deep into history before the Universe was created).
Ephesians 3:9-11 NLT - "I was chosen to explain to everyone this mysterious plan that God, the Creator of all things, had kept secret from the beginning.
God's purpose in all this was to use the church to display his wisdom in its rich variety to all the unseen rulers and authorities in the heavenly places. This was his eternal plan, which he carried out through Christ Jesus our Lord."
THAT . . . is unbelievable. If we take this concept above, highlighted in red, and apply it to the full Story of God, the implications are staggering. Yes, I am saying that we are something like a living play for the rulers and authorities in Heaven to watch and marvel over. Why? Because the Lord has a pre-written Plan, and it is being executed . . . perfectly. We are on full display to the Rulers and Authorities of the Heavenly Realms.
The Law: Part of God's Plan was to take the very small Nation of the Jews and demonstrate His Raw, almighty power through them (and others, like Pharaoh in Egypt). This Plan involves giving the Jews the Law as a protective guardian, as Paul teaches. This Law, however, would only last until Christ. When Christ fulfilled the Law, it was no longer considered an option, lest the torture and death of Christ be rendered useless.
If we study the full Story of God, the Bible in a timeline, chronological way, we will understand the Law (as much as the Lord reveals) much better than otherwise. It is simply a part of the Plan of God, where He chose to give the Blessed Jews a most Holy, and beautiful Law, such as that of Moses. Power . . . this is about Power! God did all that He said He would do through His Covenant with king David. Jesus Christ finally came as the anticipated Messiah, Jesus was killed and raised on the third Day, and the Law subsequently came to an end, for Paul teaches that anyone who attempts to be justified by the Law remains under the Lord's Curse, and at minimum, the Adamic Curse. But again, the point is that all of these things have come true. God wants us to see His Power, for He is constantly reminding us of it . . . especially throughout the Old Testament. God, apparently, is the only one allowed to boast! And He sure does, like none other.
It seems to me that this is about God having an Eternal Plan, it is being fulfilled, and the fact that God is accomplishing it perfectly, is making those Rulers and Authorities in Heaven quake in their Spiritual boots.