@mystery-ak I have been to those conventions and it is the Rules Committee or the Platform committee that did that. The National Chairman, selects the Rules and Platform committees.
When Romney was the candidate, one of his lawyers was in the Rules Committee room and caused a rule to be passed that allowed Romney to approve or throw out, any delegate. My friend was a member of that committee and tried to get them not to approve that rule the Romney lawyer wanted; she did not prevail. As these things happened, she was sending me emails. Some of the Rules committee were stuck on a bus (don't remember why the bus could not get there) and not there; that is when they took the vote to approve that rule, when a number could not get there for the vote.
When the rule was before the entire convention, Reince Priebus himself took the vote, and the nays were much louder than the yeas, and he said the rule passed. There were screams of disapproval when he did that. Priebus went on my disgust list, along with Romney for doing that, and there they remain.
Trump would not have to be in the Rules committee room or the Platform committee room if that is where it happened, to get that rule/platform change passed. He would just need one or more of the committee to put that it up for a vote. I wondered why this rule/platform was passed, why do anything to help the Russians? Somewhere there is a list of those on the committee at that time. Someone knows how that happened.