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Kei cars are the antithesis of the big American SUV. Where EPA regulations effectively penalize automakers for building smaller, more efficient cars, Japan’s Kei car regulations cap size, weight, and power to just fractions. Kei cars aren’t just small, they’re also pretty cheap, a fact that has made them a sales success in Japan and highly desirable as a grey-market import, particularly by people who think new cars have gotten too large, too complicated, and too expensive. A few years ago, Ars even wrote a guide on how to go about importing one from Japan.

But not everyone is a fan of the diminutive Kei import. As far as the federal government is concerned, as long as it’s more than 25 years old, an imported car does not have to comply with federal motor vehicle safety standards or fuel economy standards; just makes sure you pay all your import duties.

That’s because the federal government doesn’t license vehicles to operate on public roads. That task belongs to the individual states, and increasingly they are giving Kei cars the thumbs down—sometimes even in cases where previously those cars posed no problem.