That is not copyright but a geographical trademark. And trademarks are for the protection of consumers. Champagne is a type of sparkling wine made in the region of Champagne, France. If it isn't made in Champagne, France it, by definition, is not champagne. It's sparkling wine.

And this almost always comes with reduction in quality. A premium product gets watered down and Walmartified. Happens with cheeses or any other fancy foodstock.

Refusal of United States to recognize European geographical quality marks was one of the reasons why TTIP trade agreement failed (that together with United States wanting Europe to severely reform its legal base for the betterment of American corporations).