Originally Posted by alexmt

Worldwide, Amex doesn't face the same regulation because they aren't considered to have undue influence on the market. If a merchant doesn't take Amex, it's not going to cost them much, if any, business. If a merchant doesn't take Visa or Mastercard, that will hurt their business. Thus, they face stricter regulation.

You may claim there is no grounds for a lawsuit, but Australia's consumer protection (or in this case, merchant protection) group has ALREADY sued Visa over not allowing Dynamic Currency Conversion - https://www.accc.gov.au/media-releas...ainst-visa-inc

THIS is why Visa and Mastercard allow the practice, they're heavily regulated in most of the world. Discover/Diner's and Amex are not since they're not seen to be able to control the market in the same way. This is also why Visa/MC interchange is heavily regulated and Amex isn't.