In germany, and none of this is a joke, I can't legally use pedal reflectors on my bicycle that fullfill usual ISO or DIN (german ISO) norms if they don't have the stamp of approval of the Federal Bureau of Cars. I'll admit it's basically unenforced, but it does pop up in fringe cases where "was it maybe your fault for being on a bicycle when somebody pulverized you doing 100 over the limit in their SUV" when that doesn't immediatly go to be resolved as an act of god.

Further, parts for engine powered vehicles (excluding E-Bikes, without getting into the details) can be self-certified if a certificate is needed.

What I'm getting at is: While this isn't hard to circumvent on a purely mechanical case, I'm pretty sure it'll be a bitch to circument "legally"