Actually, this doesn't "punish" anybody in the sense of excluding them from the Sacraments. It excludes the Sacraments from the Campus. Anyone can go off-campus to Mass, and of course I'm hoping thousands will.
The Bishop has canonical authority to do this, and do it quickly. As I understand it, it doesn't take a lot of rigmarole from Rome or anyplace else. No person is named. A PLACE is named. And the Bishop has total, undisputed authority to say where Mass and the Sacraments CAN and CANNOT be performed in his Diocese.
The person who would be to blame for the interdict would be the President of Notre Dame, not the Bishop imposing the interdict. There are Catholic churches in South Bend that will pick up the slack until Jenkins and his cronies repent.