When a group of parents are working on building a parent group, what are the rules they should follow prior to their establishing a set of by-laws?
Does/can a principal tell a group of parents that they can not have/establish a parent group to support the students at their kids school?
Once a group is established and recognized from the principal, can the principal prohibit the parents [only a select few] from having a parent group?

I can't see why a principal would want to prohibit any PTO from being at the school...unless they felt the PTO was not following the directive of helping the kids. Perhaps there is more to the story that is unclear from your post...

ok..trying to clarify what is unclear.. one officer of the pto made an accusation against another officer. The accusing officer presented no proof or grounds of their accusation. this officer also went all over "mouthing" their accusation and refused to sit down and meet with ALL officers present.
The accused officer [treasurer] offered ANY/ALL evidence to support that the accusation was false/untrue. The burden of proof was met by the accused. [handed in to principal, gone over by multiple members of PTO and found that there is no problem with books]
The accused officer as well as the other officers are not being acknowledged by the accusing officer nor the principal [ as far as they are concerned it seems, the accused officer is no longer an officer/member of the pto] as being existant. When they are asked to provide at the least a reason for such, they refuse to, won't meet and the 1 officer is carrying on PTo business after the principal has ceased ALL Pto business at this time stating he doesn't want to deal with it.
Does this help to make it clearer to understand?

NO IT JUST MAKES MY HEAD HURT!
I SEE WHY SO MANY PTO'S HAVE A
BAD REPUTATION.
THIS REALLY LOOKS LIKE A BUNCH
OF 6TH GRADE GIRLS.