In the Netherlands, psilocybin mushrooms are illegal to possess, sell, or trade. Using them is not punishable, but possession can be.
Grow kits are legal to buy and own as long as they do not contain or produce actual mushrooms. Once mushrooms appear, possessing them is illegal.
Shops may sell the kits, but allowing them to fruit would put you in possession of illegal mushrooms.
For a short overview of the Dutch rules, see this explanation: psilocybin in the Netherlands. Hope this helps.