"If I test positive for THC at work, will my company be able to fire me, or does Prop 64 provide some protection?"
Yes. Even though marijuana is recognized at a state level, Federal law will always overrule state law. Until marijuana is legalized federally, patients are given a recommendation not a prescription. Once federally legalized patients will be able to carry a prescription and the employers will not be able to terminate you for using illicit drugs Mark Wagstaff RN
Unfortunately, Proposition 64 falls short of other legalization legislation in this respect. No, Proposition 64 does not provide you with employment protection if you test positive for THC at work.
In fact, the text of Proposition 64 specifically states that it "allow[s] public and private employers to enact and enforce workplace policies pertaining to marijuana."
This is one of many examples of the "clean up" bills that will likely be introduced after the election to ensure that Californian's personal liberties aren't limited solely based on for whom they work.