How is marijuana regulated/distributed in legalized countries?

I was wondering if someone could give me an example of the distribution chain (from grower to consumer) for marijuana in a country where it is legal. Are there wholesalers? Can I take a factory tour like a brewery or distillery for alcohol? How is it packaged? How regulated is it by the government? Do the retailers have to have licenses and permits? Just curious about the bureaucratic side of it, if you will.