The Visa/MC are stricter than that. They specify that the customer has to be presented with a clear choice with no preferential treatment given to DCC. That would knock 90% of the DCC offerings I've seen out of compliance:

• Automatic opt-in to DCC - no currency preference or even an implicit currency preference (such as writing in a tip in local currency) results in getting hit with DCC
• Confusing/convoluted methods to opt out - eg) Print next receipt?, ENQUIRY?, USD/HKD 0.122 OK? - where you have to press no/cancel or some other non-intuitive button
• Flag of card's currency takes up 90% of screen with a big OK button and a message "For HKD press HERE" shows up at the bottom in 8 pt font

The vast majority of DCC offerings I've seen wouldn't pass muster with Visa or MC if they actually cared about enforcing their regulations. But it's just like in the EMV thread. We read reports of some European merchants saying, "Sorry, no 'American' cards accepted." Others say non-PIN/non-EMV transactions are refused even though there are accept-all-cards policies. Some merchants stateside will refuse to complete a credit card transaction without ID which is against payment network policy if the card has been signed. Rarely do the payment networks enforce these rules.

I've said it before, and I'll say it again... I think the biggest culprits here are the acquirers. They stand the most to gain from the DCC scalp, and they are off the hook when a customer files a Reason Code 76 chargeback. It's the merchant's problem in that case. However, in the vast majority of cases where customers are duped into accepting DCC the acquirer makes a healthy profit on the exchange, throwing a pittance to the merchant for helping perpetuate the scam.