Yes it is legal:
"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
"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.