Reservation situations are totally different. They are not only allowed to have their own police forces, yet it would take a federal marshall to even go onto any reservation.
Yet each even have their own treaties with the federal government.
As to why they where detained off the reservation, that as well depends on treaty agreements.
I know this very well having once lived on a reservation, not all that far from San Pasquale itself. Yet I was present on the reservation during a federal raid. The US marshal had to deputize county sheriff's to conduct the raid.
You're basically dealing with a situation similar to a foreign government. Or like an ambassador situation. Enforcement depends on the treaties.
