
To be fair to Karl Malden, his commercials were for AmEx traveler's checks. I wonder if those will work in dispensaries?
Yet another reason it is so important to build support for the bill forthcoming from Rep. Jared Polis which provide banking rights for these state-legitimate cannabusinesses.
(Business Insider) Starting April 30th, consumers using their American Express cards to buy medical marijuana received notice that their cards were declined. The rejection of the cards is due to American Express’ decision to no longer allow purchases of such products with their cards. American Express made this move despite the fact that the purchase of medical marijuana is legal in 15 states.
So far, American Express has given no reason for the new rule, leaving medical marijuana dispensaries and their customers guessing at possible causes. One theory is that the card issuer has received complaints from companies about their employees using their American Express cards to purchase medical marijuana. American Express may also have received a high number of fraudulent or unauthorized charges from medical marijuana dispensaries due to people using forged or stolen cards to obtain pot.
Remember how often we get demonized as couch-surfing slackers who would drain American business productivity should our favorite herb be legalized? How is it we are getting American Express cards?

Contact your elected representatives and urge them to 'Stop Arresting Marijuana Smokers'. 
I had 2 amx cards with a 18,000 limit years ago, until they violated OUR trust and refused payment on a check I wrote on one of my accounts. Mind you, I had my accounts for over 20 years with no late pymts.
I canceled the AMX account the next week. They have been trying ever since to get me to come back,, nope.
I have TWO AMEX cards and I smoke pot!