contacting the player while on the mission. The rule was specific to the recruiting of players by coaches from teams they were not committed to prior to the mission.
Even today, a player on a mission can choose to attend a different school and participate in athletics at that new school. That is what Nelson supposedly did but that part is still allowed.
So, it's not Riley that caused it. It is more like USU caused it. They claim that Nelson was actively recruited by BYU while on his mission and that the Church School influencing a kid on a Church Mission was not fair.
Although the rule applies to all school regarding the recruiting of LDS missionaries.
While USU claims to have imperical proof of this recruiting by BYU, it wasn't out of bounds to do so at the time. Bronco said they didn't and I believe him in this case. BYU didn't recruit Nelson out of HS and very likely didn't do so while he was on his mission.
I believe Bronco has stated that he never recruited a kid on his mission as he does not want to be a distraction for the kid with things back home. I respect that and believe him as well.
I think we can thank USU for the rule. Nelson nor BYU caused the rule. It was soure grapes from USU.