Who decides Canon rules at councils in the Roman catholic church? How does the process work?
I was told something like this > at a council, the council decides. They pray about a matter of concern, and they vote. If it is a matter of what is or is not infallible, I guess they require a larger majority, but I'm not sure they require a unanimous agreement. On other matters, maybe it's only a majority vote, or it is delegated to a specialized group with expertise to handle it.
Do they get revolation from above or is it human.
My opinion >
Official Roman Catholic authorities claim they have God's authority because their popes have an "apostolic succession" which goes back to the Apostle Peter. And so, they say, they can be guided by the Holy Spirit in doctrinal and moral matters and church policy. But only certain findings are considered to be infallible. Other items are felt to be reliable since the leaders have prayed, as specially trained and prepared and selected leaders, so they are able to receive God's input and guidance.
But > my opinion > about the "apostolic succession" > saying it's so does not make it so. Even if there were Roman Catholic leaders, all the way back to the time of Jesus, this does not necessarily mean that Jesus approved them. And the ones whom Jesus did approve could have been not well-known in the history reports. But ones seeking power could have gotten the attention and mention, and even could have kept the real leaders from being publicized much, if at all.
And, to my knowledge of what is right in the Bible > 1 Timothy 3:1-10 has very clear standards given by our Apostle Paul . . . for who is qualified just to be considered to be trusted to "take care of the church of God".
I understand that the obedient succession from Peter has, all along, been obeying these standards of our Apostle Paul. And you might look at the "First Epistle of Clement" which is claimed to be by a "Pope Clement". This message nowhere names any Clement, by the way. And this message includes standards and the process for determining who is worthy to be in the true succession of Christ's church. You can see for yourself if this is a match with how the Roman Catholic leadership has done things. I personally do not find that the Bible standards and the message of "First Epistle of Clement" are a match with how Roman Catholic leadership has done their selecting of pastors and higher leaders. And I do believe the true succession is unbroken and it is obedient, with only truly Christian men all along in this succession. And to me it seems that no big-name group has obeyed these standards, but God all along has succeeded in having His real leaders laboring for Him, whether they have been publicly recognized and ordained in some group or not.
"nor as being lords over those entrusted to you, but being examples to the flock." (1 Peter 5:3)
I offer how an example is a person you know personally so you can feed on that leader's real-life example
For instance, who decided a sinner was not allowed to take communion if the person is devorced?
I think the pope can send out pastoral directives to different leaders and these get handed down to local priests.
"He who is without sin cast the first stone " and all that lol
But, also, Jesus said for the woman to stop the sinning.
Who makes these rules, do they just make them up as they go along or is this revulation from above? Who by what Authority decides?
It depends on who is in religious power, at the time. Properly, I understand, high-up Roman Catholic leaders are trusted to pray about things and then hand down their decisions and directives. But if ones are not Christians, then this can not work very well. It can be a do-it-yourself discipline and prayer thing, without Jesus. And only God can make us able to tell the difference between who He wants us to trust and who He does not approve. One of Jesus Christ's "sheep" can tell the difference between a true pastor and a wolf in sheep's clothing > John 10:1-30.
But, if media reports are reliable, there are numerous people who have had predators as their priests, but they did not know the difference. And the leaders who ordained those evil men either knew they were ordaining them . . . or they could not tell the difference between a predator and a person who is living and ministering God's own love. I will offer you > if you are a Christian . . . a sheep of Jesus > the Holy Spirit makes us able to "smell" the difference between someone who is a betrayer of children and a person who ministers the effect of God's own love to us. And you as a Christian, also, can spread the effect of God's own love in your prayer and your example and all you do in love.
So, with Jesus you can tell if someone is helping you become more real with God, and corrected to be loving any and all people, with hope for any evil person, at all . . . like Jesus on the cross had hope for any and all people. So, in case there are false people in the Roman Catholic hierarchy, we need to pray for them and have hope for them . . . not welcoming an excuse to look down on them. Do not let evil decide how we are and how we see people

or where your attention goes > first, we need to evaluate our own selves, seeking our Heavenly Father's correction.