https://www.bleepingcomputer.com/news/security/steam-blocks-dutch-users-from-trading-cs-go-and-dota-2-items-to-avoid-legal-action/

As of yesterday, Dutch owners of Counter-Strike: Global Offensive and Dota 2 are being greeted with a news message on Steam stating that they are no longer allowed to trade or perform marketplace transfers for items related to these games. This is due to Dutch law that found certain Loot Boxes to be considered gambling.