Here's the deal

In California, if you have a valid medical reason for smoking weed, and a note from the doctor stating this, you can legally buy and possess weed as far as the state of California is concerned. It is still illegal on the Federal level though.

So, if you're walking down the street with an oz of stinky weed in your hand and a local cop, say San Jose PD for example, sees you, you just pull out your doctors note and/or id card and he'll walk the other way, he can't bust you. On the other hand, if you are in one of California's National Parks, like Yosemite, and a ranger catches you, you will still be arrested because the National Parks are under Federal jurisdiction and State Law doesn't apply.

Since sick people need a place to buy thier weed, and not have to worry about getting ripped off in some shady part of town, the State has also legalized the Cannabis Clubs. Basically these are like stores that sell weed. You walk in and their are all kinds of different strains displayed. I've heard some clubs have 60 or more strains at a time. You can pick and choose what you want, sativas or indicas, or crosses of the two. Unfortunately, due to zoning restrictions these clubs are often in pretty shady parts of town themselves. And, like already mentioned, you have to show your id to get in past the burly security guy at the door.

Again, these clubs are legal as far as the State is concerned. They are still illegal as far as the Fed is concerned so the DEA can, and does, raid them from time to time. So far, however, most of the raids have been on clubs with supposed ties to organized crime. Not sure what would happen if the DEA raided a club while you were in it. Probably depended on their mood and what you looked like. If you were an oviously sick cancer patient near death, they'd probably let you go. Card carrying Republicans would probably be let go too. If you had long hair, a Dead shirt, and claimed to use it for "migraines", howver, they just might give you a hard time.