Exit Wounds - S5-E21
Factual error: The BAU is called in to assist the Sheriff's Dept. in Franklin, Alaska (a made-up town, although there is a ghost town by that name). By statute, Alaska has never had any Sheriffs. Functions filled by sheriffs elsewhere fall mostly under the auspices of the Alaska State Troopers. Other law enforcement is by community or (rarely) borough which is what Alaska has instead of counties.
Chosen answer: Black SUVs are common police, military and dignitary vehicles around the world. It is not too much to assume they could be rented or owned by the police forces in the areas.
kristenlouise3
Other people have explained it but fore more information, federal cars would most likely be brought to the airport from the nearest agency, so they can drive out to their locations especially in rural situations.