You cannot take a handful of legally prescribed pain meds, show up at work, and potentially put other people at risk. Nor can you show up at work after smoking a bowl, and work while under the influence.This is interesting, you are right about California, but in Conneticut, Maine, Rhode island, Delaware, Illinois & Arizona, you can not be fired for using medical Marijuana. I guess it just depends how the legislation was written.
http://www.mondaq.com/unitedstates/x/258244/employee+rights+labour+relations/Employer+Liability+Under+State+Medical+Marijuana+Laws
Employers cannot discriminate against you because you have a med marijuana card....but they don't have to hire you. There will be other, more "well qualified" applicants to choose from.
It's all a very slippery slope. Just try dealing with employers when one of their employees is prescribed medical marijuana, as a result of a work comp injury....It wasn't fun!