Chris Good isn't sure:
It's unclear what would happen if California did legalize marijuana. The ballot measure doesn't legalize the substance completely throughout the state: it allows for counties to legalize on their own, creating what the ballot initiatives backers hope would mirror "wet" and "dry" counties elsewhere, in which alcohol is legal or illegal.
At the end of the day, it could come down to manpower. If the measure passes, county cops can enforce the laws of their counties, while federal law enforcers could come in to enforce the Controlled Substances Act. If many counties legalize, it could come down to whether the DEA and FBI have enough officers and the inclination to enforce marijuana's illegality in California while there's a drug war raging in Mexico that's already demanding drug-enforcement resources.
2006-2011 archives for The Daily Dish, featuring Andrew Sullivan