There is much turmoil among different groups on this question. It is believed by many that having the "card" and the concealed carry permit at the same time is fine. Then, once you use the medical card, is when the issues come into play, since now you are likely violating federal law.
My uninformed opinion is that I would not want to be a person stopped for (alleged) possession at a time I had my concealed weapon on me.
The above is not intended to be legal advice, but may be used for general information. Please contact an attorney for specific help tailored to your needs. www.figgardenlaw.com
The answer right now is no, but this is a bigger issue than an AVVO answer can provide. BATF issued an opinion letter that essentially deemed holders of medical marijuana cards to be prohibited persons under federal law, who may not possess firearms or ammunition (link below). The thinking is that controlled substance use is presumed and marijuana is still prohibited under federal law. Additionally, those cards may be reported to the FBI NICS division. If the card has been reported to NICS, the holder will be deemed a prohibited person. Once a person makes the NICS prohibited person list, they will be denied on any firearm application that requires NICS approval.
This is for general informational purposes only. It does not constitute legal advice and does not establish an attorney-client relationship.