Why did the Judaizers say Paul lacked the authority Peter had?
The Judaizers claimed Paul lacked Peter's authority because Paul had not walked with Christ for three years as Peter and the twelve had. They argued apostolic authority depended on accompanying Jesus during His earthly ministry, so they dismissed Paul as an imposter and a turncoat against the traditions of the fathers.
Les explains that Paul was under constant attack from the Judaizers, who accused him of being an imposter and a turncoat against the traditions of the Fathers. Specifically, they said he did not have the authority Peter had because he did not walk with Christ for three years like Peter and the twelve did. Paul therefore continually defended his apostleship, declaring that he was an apostle not appointed by any group of men but by God Himself.