Pot has been legalized in California for medical purposes for quite some time. Although the state deems it legal the federal government does not. And there's the rub. If a federal agent finds you with pot in whatever state you live, do not pass go, do not collect $200, got directly to jail.
I understand that federally, it is still prohibited. However, without WA and CO being the first to start legalization, then the chain reaction of events toward ending this unjust prohibition would possibly not be started as it has been now.

http://www.golocalprov.com/news/pot/