You have this the wrong way round. Legalisation _does_ involve bringing something into the same set of regulations that applies to everything else, and that's a good thing. However, when we speak of "decriminalising" something, we usually mean removing criminal penalties for something that can still be against the law, and can still result in fines and other penalties. This means that the industry remains underground, which is usually worse for all involved. See the links I gave upthread for citations and the NZ context.