Me genoito ! Paul says (Galatians 2:17) to the question above. But how does the issue even come up? Why would anyone begin to think Christ is a deacon of sin?
The logic becomes clearer (though not crystal) when we take note of the syntax of Galatians 2:15-17. Verse 16 begins with a subordinate clause governed by “knowing,” and ends with two relative clauses ( hina . . . hoti ). The skeletal logic of the verses comes to view when we follow the finite verbs: “We by-nature Jews and not sinners out of the ethnicities . . . we into Christ Jesus believed so that we might be justified . . . . If seeking to be justified in Christ we also found ourselves sinners, is then Christ a minister of sin?”
Note that the thought begins with the denial that the by-nature Jews are sinners. “Sinner” is a category reserved for those who are by-nature Gentiles. By the end of verse 17, though, they have found themselves to be sinners. How does that happen? How did they discover that they are no better than Gentile sinners?
Apparently, they discover their status as sinners in seeking to be justified by Christ, that is, in the process of receiving Jesus as the Messiah of the Jews. If by becoming Christians, they discover they are sinners, does that mean that Christ has made them sinners? Paul says No, resoundingly.
And his No means that those who are by-nature Jews were already sinners prior to believing in Jesus, while they were still under the law. Verse 17 thus supports and extends Paul’s contention in verse 16 that no flesh is justified by law. Jews - Christian Jews, at least - know this already, Paul says. But what they did not know before seeking justification in Christ was that they were sinners . Until they believed in Jesus, they didn’t realize that all, Jew as well as Gentile, were shut up under sin.
Paul wouldn’t then attempt to re-erect the law that he had destroyed (v. 18). To rebuild the law that has proven itself incapable of justifying, incapable of producing anything but “sinners,” would be a transgression. Paul instead proclaims Christ, in whose faith alone one can find justification.