In our neighbourcountry Netherlands, they sell marihuana legally in the local coffeeshops where you can use it in public too. There's not really a big problem with it.
There are some problems with it: the coffeeshops are allowed to sell marihuana, but they are not allowed to buy it. They're also not allowed to grow it in the quantities necessary to do enough business. So the growing of marihuana is for a large part in the hands of criminal organizations. This fact is then used by some people to argue in favor of banning marihuana again, ignoring the fact that the problem is the half-baked current policy. (None of this is in the law btw, it's just the current policy to allow the coffeeshops.)