IIRC The Dutch government eventually auctions of everything they impound that's legal. And the law on electric skateboards and scooters as it is now here is: legal on your own property, illegal on public property. So it looks weird when they sell something that seems illegal, but it owning it isn't illegal. Using it on the road is.
Still fucked up to impound them in the first place, a fine and a warning to only use it on your own property would be enough.