Portfolionation, you seem to be confusing "the card", or at least I'm not sure which card you are talking about.

To be legal in California you don't need any card, that is just a popular myth. The reality is that to be a legal medical marijuana patient, all you need is a written recommendation from a licensed doctor. If you are arrested, all you have to do is show your recommendation to the judge, they call and confirm his license is still active, and if so, they drop any charges against you.

However, to protect patients California also wrote in a mandate that requires all counties to provide official cards for medical marijuana users. In theory, these are intended to bring protection to medical marijuana patients, but this is a theory I personally do not believe. Either way, the card seems to be popular among patients because it has helped some people by avoiding arrests, but because no time was set for how quickly a county must begin distributing these optional cards to patients, many counties have drug their feet with producing them.

But the card is completely optional, and is not legally required, I am legal but do not have one, (or want one). Some doctors who specialize in writing medical marijuana recommendations offer cards, mostly as a gimmick for advertising, but in theory some argue they could offer security, but make no mistake, the cards offered by doctors are worthless plastic, they have no real legal value. That card, too is optional.

But official card or not, I am not aware how having either of these optional cards could possibly be found in a background check. I'm not saying I think it's a good idea to have the government keep you on a list as a medical marijuana patient, but I'm just saying I'm unaware of any news that so far this has been an issue for people working in government jobs. As far as I know, currently this privacy within the state has not been compromised. And because it is a state list, no federal official even has access to that list as of now so I'm not sure how federal employees could possibly be affected.