If proposition 19 pes, how soon after can Californian's start consuming cannabis - Legally?

Cannabis will remain illegal under Federal law even if Prop 19 pes. The US Attorney General has indicated that the DEA and other Federal law enforcement agencies will resume enforcement of that portion of the Controlled Substances Act in California if Prop 19 pes. While possession and / or use of certain amounts of cannabis may not be a state crime, it will continue to be a Federal crime.