No specifics released on how to enforce it.
https://stnonline.com/news/iowa-one-...-school-buses/
"In Montana, Cohn said that school bus drivers are not responsible for students who don’t wear their seatbelts. He said that as long as drivers make a reasonable effort to ensure the students buckle up, such as walking the bus aisle and scanning for belt usage, they have met their responsibility. He said that law enforcement in Montana wants bus drivers to be focused on driving, and not focused on enforcing seatbelt policies while behind the wheel."