The Dutch coffeeshop model perfected with an auction.
The auction model works as follows. The growers and traders bring their produce to the auction. In this center of expertise the marijuana is inspected and packaged.
In the following step consumer outlets buy their merchandise at the auction. This way everybody pays taxes, the production chain is structured, and the quality is ensured.
The protection of public health would forbid advertising for cannabis products and restrict selling to adults only. (Originates from Jeroen Bos te Utrecht)