But I can replace any part on my bike with a non-CVO part and sell the CVO part to anyone, and there's nothing they can do to stop that. I think it's not only kind of ridiculous, but I don't remember signing anything that says that I agree to give them back a part if I replace mine with the same one. Something about this just doesn't seem legal.
Who knows, it probably isn't legal. But legalities haven't stopped the MoCo in the past from trying to force people to use their products for maintenance, or from denying warranty coverage over bogus "modifications" or alleged abuse. They seem to have a corporate philosophy of doing as they please and forcing the consumer to fight them. Until someone actually does fight them over this policy nothing will change.
I can see requiring a dealer to submit the VIN number the part is being ordered for, to prevent dealers from stocking restricted parts and selling them to anyone walking in off the street, but that doesn't insure the parts won't get into the hands of the wrong folks. As much as I hate to say it, there probably are a few dishonest Harley dealerships out there that would just use any CVO VIN to order parts they would then sell to anyone off the street. As some have discussed on this site in the past, people have used other folks VIN's to order parts for their non-CVO bikes. Without sending the original part back, I don't know of a way to control this. If anyone has a better idea to control the so-called exclusive parts, please submit it here and directly to the MoCo. In the meantime, feel free to sue them when they won't sell you a part unless you give them the old one. Until someone does so, they will continue to do as they see fit.
btw, you could always remove the subject part and then ride over to the dealer and try to convince them the part fell off. It would be a little tough to do with a fuel tank, but a badge from an air cleaner or tour pak could fall off or be stolen quite easily.