I have a friend "Steve" that sells CC processing for a company called Beyond. Beyond has been successful in selling this charging concept in California and nationally as well and unfortunately it is legal. The fee charges are the brainchild of Beyond CEO Robert O Carr. In my view the fees are simply a sales/marketing ploy to get more merchants. Beyond's sales pitch is "Why should a merchant pay CC charges so some "bleep" can fly for free.
Steve and and I have been arguing about these charges for the last couple of years. Steve swears his merchants hear no complaints about the additional charges from customers. My point is that many customers notice the fee and don't complain simply take their business elsewhere. I believe customers are more cost savvy than Beyond is giving them credit for.
My guess is we will see more and more of these CC charges in the future. When I see charges tacked on to purchases my response is to share my thoughts with the merchant and take my business elsewhere.
Best
Guido88