are you not supposed to sell "grey " tractors on ebay?
The fundamental legal issue is that the owner of a copyright or trademark has a legal right to control ALL use of that trademark.
Some companies hire continuous automated searches to find every appearance of their trademark.
Ebay's VERO program closes auctions after receiving a complaint from the trademark owner. (They have to, or they could be sued for aiding the illegal use).
Yanmar-USA has a list on their website showing models they never sold in the US. Whenever an auction appears showing one of those model numbers, VERO steps on it.
Most companies don't enforce their trademark so intensively but there are a few that do. I recall a similar example on ebay where the US importer of a brand of camera lenses blocked all sales of used lenses labeled with the brand he had exclusive rights to.
And why does Yanmar-USA have such an attitude about this? They lost a lawsuit and had to support the widow of someone killed on a gray-market Yanmar. The plaintiff showed that parts to maintain the tractor were available from Yanmar-USA, so they were benefiting from these imports. Yanmar-USA has subsequently tried to cut off all relationship to models they never sold in the US.
Kubota is even worse. They have a standing order that any gray model Kubota that arrives on a US dock will be refused entry by Customs. It will sit on the dock (with storage charges, no doubt) until somebody pays to have it re-shipped to a foreign destination. Obviously this is a disaster to the attempted importer.
While all this seems strange, it is all US law. Good luck trying to get the law changed.