No you can not. You are still considered an illegal user according to the federal government and the questions on the CCW application (which are taken from ATF form 4473), or commiting felony perjury by answering no to question 11. I have discussed this with ATF and CBI. MMJ card = no posession of a firearm. Period. I know people are thinking, "how would they know? What is under the influence? etc...) CBI is in process of creating a database for MMJ card holders and this will be cross checked with CBI checks. Posession of a MMJ card can be considered under the influence as, depending on the test administered, the drug can be in your system for as long as 1 week or more. I don't know of anyone who has challenged this as of yet, but expect big guns on the side of ATF, CBI, and State of CO if this does go to court. Direct word I have recieved from ATF is MMJ card = no transfer of a firearm as indicated on Form 4473, question 11.
On the common sense side: Would you REALLY carry when medicating? I hope not...