Can California employers fire medical marijuana users?

The California supreme court will soon rule on whether employers have a right to fire employees who test positive for marijuana on drug tests, even if they have dispensations from doctors to use medical marijuana. So far, the prognosis doesn't look all that great for medical marijuana users in the state:

Two lower courts have sided with Ragingwire's decision to fire Ross because federal law holds that marijuana is illegal in all guises.

Five current and former Democratic state legislators who argue that the lower courts misinterpreted a law they helped pass that banned smoking of medicinal marijuana at the workplace. The lawmakers said nothing in their law prevents employees with medical marijuana cards to smoke outside the workplace.

The lawmakers wrote that the state's fair employment law and the 1996 Compassionate Use Act legalizing medicinal marijuana, "authorize and protect the use of medical cannabis by employees away from the workplace and during nonbusiness hours, as exemplified by plaintiff-petitioner Gary Ross, and that the court of appeal's decision erred in concluding otherwise."

Employers are fearful of falling productivity and that they open themselves to the wrath of federal officials, who are armed with a 2005 U.S. Supreme Court decision declaring that state medicinal marijuana laws don't protect users from criminal prosecution.