Transgression in Paul’s terminology refers to violation of specific commandments. Mostly. But Galatians 2:17 has a radical redefinition of transgression. J. Louis Martyn says, when Paul says that re-erecting the wall of separation between Jew and Gentile makes him a transgressor, he implies that “the Law can play a role leading not to the defining and vanquishing of transgression, but rather to transgression itself! . . . whoever reerects the Law’s distinction between Jew and Gentile, as thought God were making things right through observance of the Law, rather than in Christ, has thereby shown himself to be a transgressor.”

Transgression is usually boundary-crossing. But Paul says that in the new covenant transgression can take the form of erecting boundaries. And he is also implying that transgression is not judged by timeless moral standards, but is redemptive-historically qualified.