Now, which James was this?
James the son of Zebedee?
James the son of Aphaeus?
Or, yet another James?
James, the son of Zebedee was beheaded by Herod - Acts 12:1-3
From the Catholic Encyclopedia (but stay tuned - because some good ol’ Catholic teaching on the Council of Jerusalem follows

):
"The James (5) of Jude 1:1 must certainly be identified with James (3), the brother of the Lord and the Bishop of Jerusalem. The identification of James (3), the brother of the Lord and James (4), the son of Mary, and probably of Cleophas or Clopas offers some difficulty. This identification requires the identity of Mary, the mother of James (Matthew 27:56; Mark 15:40), with Mary the wife of Cleophas (John 19:25), and, consequently, the identity of Alpheus (2) and Clopas (4). As Clopas and Alpheus are probably not two different transcriptions of the same Aramaic name Halpai (see CLEOPHAS), it must be admitted that two different names have been borne by one man. Indeed, there are several examples of the use of two names (a Hebrew and a Greek or Latin name) to designate the same person (Simon-Petrus; Saulus-Paulus), so that the identity of Alpheus and Cleophas is by no means improbable.
On the whole, although there is no full evidence for the identity of James (2), the son of Alpheus, and James (3), the brother of the Lord, and James (4), the son of Mary of Clopas, the view that one and the same person is described in the New Testament in these three different ways, is by far the most probable. There is, at any rate, very good ground (Galatians 1:19, 2:9, 2:12) for believing that the Apostle James, the son of Alpheus is the same person as James, the brother of the Lord, the well-known Bishop of Jerusalem of the Acts. As to the nature of the relationship which the name “brother of the Lord” is intended to express, see BRETHREN OF THE LORD.
On to the Council:
It would seem that you, Grace, (please excuse if this isn’t the case) are trying to neuter St. Peter’s authority and leadership of the Church given to him by Christ Himself. St. Peter made the point moot in his declaration which is why “they all fell silent”. There was nothing more to be added to the conversation because it was what it was. St. Peter called the spade a spade. St. James didn’t ‘trump’ St. Peter…on the contrary, he agreed and supported St. Peter and since THIS James - James the Less - was the Bishop of Jerusalem where the Council was residing, he was being a good host to the Pope and tried to make it ‘kosher’ for those who all of a sudden ‘fell silent’. It was as if there was an awkward silence that St. Peter created with the truth he spoke. Perhaps a hard truth…BUT - since those who were present KNEW what St. Peter was - they respected him and ‘fell silent’. The Bishop felt obligated to help a brother out

and smooth it over.
However, being that it WAS a Council, even if St. James DID object to what St. Peter said (which he didn’t) then he had right to do so CHIEFLY because it’s a Council. It’s a meeting of the minds of the leadership of the Church. All Councils of the Church provide the opportunity of the Bishops and Cardinals, a.k.a. the Magisterium, - to discuss doctrine. It is then clarified for the rest…and formalized in a letter. This can be dogma which means infallibility must be invoked. Or it can be just an instruction…which after more discernment and discussion - could change - at a later date even. The Apostles were doing then what was best for the Church - and the respect is felt for St. Peter by everyone there - when they all fell silent. It’s the same sense of respect good Catholics should have for our Pope now. We might not like what Peter has to say - it might hurt - but what the Pope says is respected and good Catholics fall silent and humbly obey. We don’t assert ourselves as our own popes and declare the authority Christ gave to Peter alone invalid when it hurts…out of respect for the office of the Papacy - we too fall silent. That is what you are witnessing…right there in Scripture.
It’s an amazing passage for us Catholics to look upon. Because you have the Council taking place in which you have discussion over what should happen. The Pope is the one who makes a judgement under collegial agreement - and the Bishops translate it for the people with the Apostolic gifts given them. Then there’s a letter - is this like the first recorded encyclical then?
To the T - it is the structure of what occurs TOday…and began 2000 years ago. Glorious…Majestic…and Ancient is the Church Christ established…that gates of hell itself have never prevailed against.
God bless you,
luke1_28