The law you drive under
Driving in Nepal is governed by the Motor Vehicles and Transport Management Act and the rules made under it. It sets who may drive, what a vehicle must carry, and what happens when either fails.
Three things must be valid at once: your driving licence for that class of vehicle, the vehicle's registration (bluebook), and its insurance. A route permit is required as well for a public vehicle.
The rules are enforced on the road by the traffic police and administratively by the Transport Management Office. The first can stop and fine you; the second issues, renews and can suspend what they check.