"Beginning January 27, 2013, merchants in the United States and U.S. Territories will be permitted to impose a surcharge on consumers when they use a credit card." http://usa.visa.com/personal/get-help/checkout-fees.jsp
It's good that governments still have a bigger stick they can use to beat some sense into corporations.
I'm pressed for time at the moment, so I can't provide a link.
It seems to me like there's three contracts involved: The agreement between merchant/CC, consumer/CC, and consumer/merchant. Since these are all private parties, why does the government even care what contractual arrangements they make among themselves regarding how the form of payment affects how much needs to be paid?
You can say "if you are dressed like a clown today we will give you a 10% discount". Point being that there is nothing to prevent you from giving someone a discount as long as it doesn't break any laws and as long as you are offering it to everyone that falls into the same category (or the discount has been negotiated).
In in the fine print it was clear that offering your customers a cash discount was grounds for immediately canceling your ability to take credit cards. If I recall rightly, I noticed because the store I was at did indeed offer a discount. In practice, I'm sure the store was small enough that VISA didn't care. But for larger operations I'm sure it was a serious threat.
I believe they were eventually sued and lost, but since I rarely see discounts like that, I imagine they have some sort of not-quite-illegal trick, like offering merchants advertising credits based on charged card volume.
http://www.ncsl.org/research/financial-services-and-commerce...