Some issues arise when people think of having a MMJ card as freedom to smoke whenever. I listen to a radio show that has a lawyer come in and give advice once a week, and you wouldn't believe how many people call in pissed off that they got a DUI while high. "But I have a medical MJ card!!!" Morons.

That being said, its no different than if you were drinking and carrying...I don't think you'd have any issue having a CCW permit and a MMJ license, as long as you're not doing one while doing the other.

Just as you can't drink while carrying, if you don't smoke while carrying you shouldn't have an issue.

I also noticed that when doing a firearms background check, you could also make an argument that you are not an unlawful marijuana user (as stated on the form).

Disclaimer: I don't do drugs but advocate the regulation and taxation of MJ.

Edit: I didn't read before replying, so that's interesting that it is considered unlawful. Oh well. Get drunk instead!