It depends on what you have looked at as being organic, I've seen plenty that are pre-made and are actually organic, but it may depend on what your specific criteria are and if you are looking for organic or just any pre-made soil options.
I don't think the method of growing a specific crop may be illegal, but the crops you are growing and what you are doing with them could possibly to illegal depending on how you got the seed(s).
I would mostly use a weed based killer, but I don't think if I was ever going to eat the plant or use it in another means that I would not trust or use any pesticides.
I don't know that many who just use it as food, others I know use them to make medicines, to keep specific arrangements in their landscape, and other times I've known them to keep their fish tanks clean (although, that is another subject).
There are a handful of different farm locations based near me, although I've seen them to mostly just grow cactus, palm trees, and other low water usage plants when compared to ore of a "normal" water usage from a forest based area.
I think this mostly is a method that is used for either desert based landscaping, or for potted plants in order to improve the ability to keep them watered enough per each container. I have a few setup in my front and back yard due to my desert based landscaping, and I'll try to snag some photos...