Yes, microdosing is 100% legal in the Netherlands. It concerns Sclerotia (underground substrate) of the Psilocybe Mexicana that simply grow in the ground. It is a natural process. As a result, the truffles do not belong to the mushrooms known for their psychedelic effects. The product therefore does not fall under the mushroom law that applies in the Netherlands.
Mushrooms are on list 2 of the Opium Act and are therefore prohibited to breed, sell or buy. The Psilocybe Mexicana is almost impossible to breed at home. That makes control easier. That is why you can use microdosings completely legally.
That’s why truffles can be shipped to all EU countries under the Mutual Recognition of Goods Principle of the European Commission.