"It is apparent that those who accused Paul of teaching things contrary to the law were actually the ones who were endorsing vain traditions that actually were contrary to the law. That's the "upside-down" scenario." . . . so bottom line - I don't see this.
I'll explain further. Paul said (about himself) that he worshiped believing all that was written in the law and the prophets. Acts 24:14b
"so worship I the God of my fathers, believing all things which are written in the law and in the prophets:" He was describing his worship by an UN-defiled law that came directly from God without any additions, or subtractions that came from a Pharisaical tradition.
"Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law,
judgment, mercy, and faith: these ought ye to have done, and
not to leave the other undone." Matthew 23:23
One must also keep in mind that physical circumcision wasn't introduced via the law at Sinai. It was a sign of the covenant with Abraham. The law introduces the circumcision of the heart, (twice in Deuteronomy, and once in Jeremiah) same as the circumcision of the new covenant through Christ.
Satan desired the law to be messed up during the time of Christ on this earth. Because that didn't work for him, today he is doing all he can to make it void. In either case the end result is the same for this
"upside-down" adversarial persuasion.
If a person would diligently observe all the law by their own strength, they would still
never be made righteous, because it is God who makes righteous, not the act of observance itself. All observance of the law teachings (Torah)
must be based on faith. Our observance is according to the will of God, and is done in a manner that is pleasing to Him.
The law given via Moses reveals our Messiah, and Messiah is the fullness of the law in its pure form. It's the Torah teachings that establish the criteria for Messiah's righteousness. Therefore,
it is impossible to be justified by the law without faith in Christ Jesus. Belief in Christ goes to the heart of faith. The law cannot be negated or else Jesus Christ would be negated as well because
they are One. Sacrifice for sin, and atonement are all established by faith in God, and all faith in God points directly to Jesus Christ.
Jesus is God's own arm who brought salvation.
"Do we then make void the law through faith? God forbid: yea, we
establish the law." Romans 3:31