Originally Posted by Poly
Well the law in Britain says yes. You need to believe it won't be used on the road not just you've told someone it shouldn't be used. I don't think you'd convince a court that you honestly believed it wasn't going to be used on the road if he turned up with no other means to get it home. That said, of course cars (and trailers) are sold all the time in unroadworthy condition and prosecutions are very unusual, especially of private sellers.
OK, fair enough. Sounds kind of tricky to sell used trailers that are not road worthy as You might end up in troubles You did not expect...
Over here any trailer intended for roads needs to be type approved, registered(trailers have own plates) and insured. If its braked, you need to do a MOT inspection every second year.
If You want to sell a road unsafe trailer, You will remove the plates. After that You are pretty safe responsibility wise if the next owner does anything stupid with it.
I always considered this pretty controlling attitude toward trailers annoying, but in some cases its maybe not so bad after all.