Rather than clutter another thread with an interesting but off-topic item I think it is worth running a new one.

Here's the basis. A chap buys a new spring rifle from a dealer in Holland. The standard spring for the Dutch market is good for 20 joules, about 15 ft.lb. The Dutch retailer knows this, and he knows the UK limit is about 16 joules, so he puts a weaker spring in the rifle before he despatches it.

As the dealer is charging extra for the UK spring and not giving a credit for the 20 joule spring, he considers both to be the property of the buyer, and so he ships the 20 joule spring in the same box as the new rifle.

The buyer receives a legit rifle and an overpowered spring (for the UK market).

Question: is the new owner at liberty to sell the 20 joule spring, to anyone?