Premium items restrictions.

You can configure the relevant settings in StrangeWorlds.eco:
"AllowPaidItemsInPlayerStores": false, (Determines if marketplace items can be sold in stores)
"AllowUsingPaidItemsWithoutBlueprint": false, (Determines if marketplace items can be used without owning them, e.g. if you can place them if you don't own them)
"BlockUsingAnyPaidItem": false, (Determines if marketplace is enabled or disabled and hence the usage of any marketplace items)

Copy the file, name it StrangeWorlds.eco and change the settings. The settings I mentioned are contained therein.