Dear Sir,
champagne is a dénomination of origin. It is a sparkling wine produced only in France in the delimited area of Champagne according to strict regulations. As such several mentions are compulsory on the label among which the name CHAMPAGNE.
This is not written on the label so Sumei is not Champagne.
Attached is a document that should answer your questions about Champagne.
Kind regards
Brigitte Batonnet
Documentation – Relations pressed