Wrong, if you have a "marijuana license" you have a marijuana license, if you can roll up that license, smoke it, and get high please post your experience here.
To make an analogy, under your example if you have CWP license and walk into an airport (unarmed) you should be be arrested on "unlawful" weapons possession charges simply by possessing the CWP license.
To clarify, in WA there is no 'Marijuana License' per say. What is required is a note from a doctor. What people are usually refer to is; because most physicians will not write a letter saying they reccomend using Marijuana, instead there are offices that charge a visit fee (usually around $200) and give you a card that has your pic and info, and on the back is a written letter stating "...under RCW----- I believe my patient would benefit from using medical Marijuana for the treatment of _____" along with a signature. Usually they are not peoples regular doctors.