Good question! You're right, this is surprisingly hard to Google. It looks like the FDA is responsible. I would not have guessed that!
The National Highway Traffic Safety Administration (NHTSA) would have been my guess, but I'm not finding much there. They have a spec for LIDAR speed measurement devices, and one for the required sensors in vehicles, but nothing on the the output of said sensors.
> For manufacturers of laser products, the standard of principal importance is the regulation of the Center for Devices and Radiological Health (CDRH), Food and Drug Administration (FDA) which regulates product performance. All laser products sold in the USA since August 1976 must be certified by the manufacturer as meeting certain product performance (safety) standards, and each laser must bear a label indicating compliance with the standard and denoting the laser hazard classification.
https://www.lia.org/resources/laser-safety-information/laser...
https://www.fda.gov/radiation-emitting-products/home-busines...
https://www.fda.gov/about-fda/fda-organization/center-device...