I'm not so sure this is an April Fool's Day joke! It sounds pretty convincing. Our youngest son's girlfriend is from the Netherlands, and she has described these places in Amsterdam to me in detail. Anything you ingest (or smoke) is totally restricted to the establishment you are visiting, and cannot be taken or consumed outside. So, you can't buy a half dozen hash-laced brownies and bring them back to the cruise ship. You could eat one while having some strong dutch coffee at the cafe, and hopefully you won't accidentally get on the wrong ship when you make it back to port!