For some time I have been thinking about how ridiculous it is that Kobe beef is even not allowed in the US and yet many people think they have eaten Kobe beef. But apparently that was only true from 2010 through late 2012 when the USDA began allowing some Kobe beef back in the country. That's good, because it means that the sushi chef who I'm pretty sure used real kobe beef to make nigiri is no longer violating that particular regulation in order to serve amazing food*.
The Kobe beef controversy is related but not exactly the same as the Champagne controversy. To many people, Champagne just means "sparkling wine." Kobe beef and Wagyu beef are used to mean "high quality beef" because people imagine that they are eating a very specific type of beef from Japan. When the beef isn't actually from Japan and isn't even a purebred Wagyu, the issue is closer to fraud.
Champagne producers already won the battle of forcing sellers to label where the bubbly actually came from. They are hoping to push their victory even farther by recapturing a term that has developed a generic meaning. The Japanese beef lobby hasn't even begun to mitigate the fraud perpetuated by the US beef and restaurant industry. So even though it's actually possible for people to import Kobe beef, think twice before you order Kobe beef in a US restaurant. It's probably not the real thing, especially if it only seems mildly expensive.
*Maybe I'm not cynical enough, but it seems like people who import other high cost food from Japan such as fresh fish would be more likely to serve the real thing, especially if it is an off menu item.