I'd written a few months ago about Oregon's Monsanto Protection Act, which prohibited local governments from regulating the production, sale, and use of certain kinds of agricultural products. The Monsanto Protection Act, Senate Bill 863 in the 2013 special session, was rushed through the legislature without any particular sponsor, and was intended to prohibit cities and counties from regulating or prohibiting the use of genetically modified seeds and their products.
The act doesn't, however, refer to genetically modified seed, but states in broad terms that local governments may not enact or enforce any regulation that restricts (among other things) the sale, propagation, or use of agricultural seeds, nursery seeds, and their products. You can read the text of the act here.
The 2013 legislature also passed a law to allow medical marijuana use, and retail dispensaries ("pot stores") of medical marijuana. Several Oregon cities are working to ban retail marijuana stores from opening up shop within their limits.
If you didn't click on the link to the Monsanto Act, go back and do that now. Then consider whether the Monsanto Act prohibits cities and counties from regulating marijuana stores, at least if the marijuana is grown from seeds that could qualify as "agricultural seed," "nursery seed," or "vegetable seed" as defined in the law. "Vegetable seed" includes "the seed of those crops usually grown in Oregon in gardens or on truck farms or for canning and freezing purposes and generally known and sold under the name of vegetable seed." "Agricultural seed" means "fiber, forage and grass crop seed and any other kind of seed or bulblet commonly recognized in this state as agricultural seed or as lawn or turf seed, and mixtures of any of such seeds, as may be determined by the Director of Agriculture."
Is marijuana seed "grass crop seed," and will the Director of Agriculture determine it to be "grass crop seed"? If so, then the Monsanto Act prevents cities from banning the sale of marijuana seeds, and also from banning the growing, harvesting, marketing, possession, and use of marijuana seeds and their products. This happy result almost reconciles me to the Monsanto Protection Act itself.