RE: Technically, the rules change at every convention because each convention votes in a new set of rules.
So, did the Louisiana delegate rules change recently, or were they in place since long before the primaries started?
Fair question.
I was referring to the national convention, but to answer your question, state party rules work in a similar fashion but vary widely among the 50 states.
Each convention, whether precinct, district, or state, votes to approve or amend the rules proposed and passed by the standing rules committee that last met. That is a very a broad statement, but is generally the way it works.
“So, did the Louisiana delegate rules change recently, or were they in place since long before the primaries started?”
Perhaps this will help to understand delegate rules:
The rules made at the national convention, only have to do with rules about conducting the convention, not about how delegates are selected for this election season.
The delegate selection process is the purview of the state parties. A state party cannot change the delegate selection process in an ongoing election season. The rules about delegate selection they had before this election season started is the process they must follow.