See The New York Times article, Cities Balk as Federal Law on Marijuana Is Enforced, for more information on the somewhat arbitrary enforcement of Federal law in California and the disarray it is creating in the reasonable regulation of California's medical marijuana statute.
This November's election, in which voters in several states including Colorado and Washington approved the legalization of marijuana has further heightened the conflict between federal and state laws governing pot use and possession. This interesting Seattle Police Department post entitled Marijwhatnow? A Guide to Legal Marijuana Use In Seattle further demonstrates the dilemma now faced by state officials, including police officers. Kudos to the Seattle Police for their brave position in the face of the currently enunciated federal law. To their further credit, the Seattle Police Department wrote the guide in a lighthearted manner, as noted by NPR in What Are They Smoking In Seattle? Check Out Police Dept.'s Guide To Pot Use, including a link to this Lord of the Rings clip: