Figure Analysis
This guy, who Paul calls "the Lord's brother" (Galatians 1:19), seems to be the head honcho at the church in Jerusalem. It's pretty clear that Paul doesn't have much love for James either. He doesn't come right out and say it, but there's sort of a veiled contempt for James and the elders in Jerusalem:
Those who were supposed to be acknowledged leaders (what they actually were makes no difference to me; God shows no partiality)—those leaders contributed nothing to me. On the contrary[…] when James and Cephas and John, who were acknowledged pillars, recognized the grace that had been given to me, they gave to Barnabas and me the right hand of fellowship, agreeing that we should go to the Gentiles and they to the circumcised. (Galatians 2:6-9)
Sure, James and his ilk are the "acknowledged leaders," but that doesn't hold much sway with Paul. He's clear that he doesn't come there to get their approval for what he's doing. He just wants them to agree not to interfere. Though it seems that James still can't resist butting in later when he sends some people to Antioch and everyone stops eating with Gentiles (Galatians 2:12).
Paul has his work cut out for him.
Galatians isn't the only place that James gets some mentions. He's called out as the brother of Jesus in the gospels ("Is not this the carpenter, the son of Mary and brother of James?" [Mark 6:3]). In Acts, he commands loads of authority in the church as the one who settles the whole circumcision question (Acts 15:13-21). (Paul tells that story just a little bit differently.)
But it was clear that James was really well respected in early Christian circles because Eusebius (a church historian) says that James "is recorded to have been the first to be made bishop of the church of Jerusalem" (source). It's no bishop of Rome, but it's nice.
Elsewhere in Christian tradition, James is called "James the Just" so folks can tell him from all the other Jameses out there in Jerusalem (oddly enough, there were a lot). Legend also has it that he wrote the Epistle of James, which seems to cause problems for Paul's idea of justification by faith.
Oh, James. You'll just never stop annoying Paul, will you?