A person propelling a bicycle or moped may ride only on or astride a permanent and regular seat attached to the bicycle or moped. This requirement does not apply to a motorized scooter.
Riding On Bicycles, Mopeds, Or Motorized Scooters
Mont. Code Ann. § 61-8-603, under Bicycle, Moped, and Motorized Scooter Traffic.
Mont. Code Ann. § 61-8-603