I don't know how it works, but I can look to a certain Nike school and order any football jersey from the official team store website, 100% affiliated with the university. Every player's jersey is listed. In fact, you can't purchase a "blank" jersey without the name on the back, presumably to get around sharing in some of the profit with the player. You can customize jerseys, but there are certain names that you can't pick (former players), unless that player has agreed to an agreement with the school or NCAA (I can't tell which). So, I don't know what BYU can/can't do with the BYU Store, just that another school has figured it out and made every jersey available.