If you've spent as much time on farms as I have, you may imagine that floating horse teeth has something to do with a backup of equine urine. It actually refers to the time-honored practice of filing horses' teeth to prevent them from getting uncomfortably long. At the behest of veterinarians (who else?), the state of Minnesota is trying to limit the service to veterinarians, and the Institute for Justice (who else?) is challenging the protectionist regulations in state court.
Should you balk at going to veterinary school just so you can file horse teeth for a living (a technique veterinary schools don't even teach*), Minnesota will give you a pass if you 1) have more than 10 years of experience or 2) pass an exam given by the Dallas-based International Association of Equine Dentistry. "To qualify to take the IAED's test," I.J. notes, "you must float the teeth of 250 horses under the supervision of an existing IAED member. Not only are there no IAED members in Minnesota, it is illegal to float without a license. So, to abide by the law in Minnesota, you must break it."
[*Both Lee McGrath, executive director of I.J.'s Minnesota chapter, and I.J.'s client, Chris Johnson, assert this in the I.J. press release, but commenter Lee, whose wife is a vet, says it isn't true.]