I had a particularly egregious case of the DCC scam last week in Switzerland. Used a German card (billed in EUR) and was given the option of paying in CHF (local currency) or USD.

Now, I hate DCC with a passion, but most jurisdictions seem to have nothing against it. But how does the already flimsy rationale of "convenience of paying in your own currency" work in this case? Allow us to convert the local currency (CHF) to a third currency (USD) at a markup, and then your own bank can convert it to your billing currency (EUR)? How's this not illegal?