I believe you cant buy and register in any of the above states. The only way to do it is buy, register in a "legal" state and do the title transfer to any state afterwards. I could easily see a spike in Montana registrations..not only to save on taxes ( keep your moral judgment to yourself please) but also to circumvent the guardrails to register in your homestate. Buy on LLC in MT, transfer in your name in any state . Problem is MT registration business that help you set a LLC hate it when ppl transfer in their personal name. The way they make their money is charging you a fee every year as long as you keep the car registered in MT