Wis. Stat. § 100.36: Frauds; substitute for butter; advertisement.

No person may use the word “butter” in any way in connection or association with the sale or exposure for sale or advertisement of any substance designed to be used as a substitute for butter. No person may use terms such as “cream”, “creamery” or “dairy”, or the name or representation of any breed of dairy cattle, or any combination of such words and representation, or any other words or symbols or combinations thereof commonly used in the sale of butter unless at least 40 percent of the substitute is butterfat. If the term “butter” is used in connection with the name of any such product, it shall be qualified so as to distinguish it from butter as defined in s. 97.01 (1r).