In dutch, this structure is called 'gedogen'. It means that when it comes to marijuana, the police doesn't prosecute, within certain bounds that is. So you can have max 5 grams of weed on your person and have max 1 plant for personal use. Also, while selling weed is OK, growing more than one plant isn't. The problem with this structure is that there is no way to regulate, since it still is, in essence, illegal to deal in these drugs. Unregulated markets can go horribly wrong. By allowing people to sell and consume drugs and not regulating the cultivation, you are in essence creating a low risk illegal market, since the investors are quite certain they can sell their goods. Legalizing indeed has its dark side, but so has keeping it in the books...