In this very important passage, Paul alludes to the doctrine of the "abrogation" of the "Old" Law, the Law of the Torah, of the Jews. To abrogate means to abolish by an authoritative action - the action being, in this case, the death of Christ.
If the Old Law has been abrogated, does that mean that, according to Paul, a Jew who accepts the teaching that Jesus was the messiah must cease to observe that "Old Law"?