An Illegitimate Division of Ministries
Gal 2:7-9 On the contrary, they saw that I had been entrusted with the task of preaching the gospel to the Gentiles, just as Peter had been to the Jews. (For God, who was at work in the ministry of Peter as an apostle to the Jews, was also at work in my ministry as an apostle to the Gentiles.) James, Peter and John, those reputed to be pillars, gave me and Barnabas the right hand of fellowship when they recognized the grace given to me. They agreed that we should go to the Gentiles, and they to the Jews.
This was one of the purposes of Paul's mission to Jerusalem - to receive affirmation by the church leaders there so as to lend supporting evidence against the circumcision. Paul needed no affirmation for himself, for he knew his calling and was confident of his gospel. But the endorsement of James, Peter and John would provide evidence of that fact to the Galatians. And it would discredit the circumcision who may have falsely claimed that they had been sent by the Jerusalem church.
However this idea that Paul alone was to be an apostle to the Gentiles while everyone else, like Peter was to go to the Jews, was contrary to what Jesus commanded, not to mention what Peter himself mentioned at that very meeting when he said, "Brothers, you know that some time ago God made a choice among you that the Gentiles might hear from my lips the message of the gospel and believe." Acts 15:7 You would think it was Paul speaking, but it was Peter!
Furthermore Jesus told Peter and John, "go and make disciples of all nations" Mt 28:19, the word "nations" here and "Gentiles" in the Galatians verse being the same Greek word "ethnos". And furthermore he told them, "you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth." Acts 1:8 But Peter and John settled into a Jerusalem ministry most likely because of prejudice against Gentiles. (Even despite the fact that Jesus gave Peter the vision to preach to the Gentiles in Acts 10 saying that "What God has cleansed you must not call common", referring to the Gentiles.)
So why did Peter give up his commission to the Gentiles at this time? I think it was simply prejudice. Seems to me it was because of prejudice against Gentiles that they had overlooked what harm was being done to Gentile Christians by those who were likely members of their own church. It wasn't until years later that circumstances (and no doubt the Spirit of God) forced them to overcome their prejudice.
And I find it interesting that while they gave Paul and Barnabas the right of fellowship, no mention was made of Titus who was also present. But he was a Gentile.