Some nitwit in an exotic car decided that meant they could go 60-70 mph faster than the convoy of 'runamuckas' they were weaving through, and ended up suing the State when they got a ticket because the statute was (as they claimed and the court upheld) "unconstitutionally vague".
Now drivers there are limited to 75 on the interstates...You used to be able to do 120 and not get a ticket, if the road and the car were right.
Look out in Missoula though, they have a fleet of unmarked black Lambourghini Highway Patrol cars. :)
I don't think that is quite right. From Wikipedia:
On March 10, 1996, a Montana Patrolman issued a speed ticket to a driver traveling at 85 mph (140 km/h) on a lonely stretch of State Highway 200. The 50-year-old male driver was operating a 1996 Camaro with less than 10,000 miles (16,000 km) on the odometer. Although the officer gave no opinion as to what would have been a reasonable speed, the driver was convicted. The driver appealed all the way to the Montana Supreme Court. The Court reversed the conviction in case No. 97-486 on 23 December 1998; it held that a law requiring drivers to drive at a non-numerical "reasonable and proper" speed "is so vague that it violates the Due Process Clause ... of the Montana Constitution". Due to this reversal, Montana scrambled to vote in a numerical limit as it technically had no speed limit whatsoever in the meantime. In June 1999, a new Montana speed limit law went into effect. The law's practical effect was to require posted limits on all roads and disallow any speed limit higher than 75 mph (120 km/h).
The decision is posted here: http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=MT&vol=97&invol=486