| Venue: | SCOTUS |
| Facts: | Iowa wants to prohibit the use of 65-foot "doubles" on its highways. This is ostensibly a safety thing, but it impacts the delivery of interstate freight, and I-80 is sort of a big deal. |
| Posture: | None evident. |
| Issue: | Is it unconstitutional for IA to ban large trucks? |
| Holding: | Yes, amazingly. |
| Rule: | A state can't promote its own parochial interests by requiring safe vehicles to detour around it. |
| Reasoning: | This impacts interstate shipping, and it's out of step with all other states' laws in the Midwest. There's evidence that doubles are as safe as semis. The worries about passing and backing up are not relevant on the interstate, and the jacknifing problem is a canard, because 60-foot doubles are allowed and they have the problem even worse. |
| Dicta: | Dissent: we should presume that state safety measures are valid. Also, since there's no such thing as legislative intent, it makes no sense to strike down a rule based on the reason it was enacted. |