Halt the margaritas! Two of your favorite tequila brands are in hot water. A class action lawsuit alleges that Casamigos and Don Julio tequilas "consist of significant concentrations of cane or other types of alcohol rather than pure tequila."

The proposed class-action lawsuit, filed in the U.S. District Court for the Eastern District of New York, goes on to allege that both brands fail to meet the regulatory requirements to label themselves as "100% agave" in Mexico and the United States, even though they carry that distinction on their labels. This is important because, according to Mexican law, tequilas that are marked as "100% agave" must be produced exclusively from Blue Weber agave grown in designated regions of Mexico.

Food & Wine explains that while tequila regulations do permit a small amount of flavoring—up to one percent of the total volume—the inclusion of alcohol from sources other than Blue Weber agave, such as cane spirits, is strictly prohibited.

The lawsuit claims that Casamigos and Don Julio contain significant amounts of non-agave alcohols, despite being labeled as “100% agave.” Customers named in the suit claim that they purchased the products under the assumption that the tequilas were made exclusively from Blue Weber agave, and paid prices reflective of that premium designation. The lawsuit seeks $5 million in damages on behalf of consumers, along with an injunction to halt Diageo—the brands' parent company—from allegedly "deceptive advertising practices."

The plaintiffs also point to wider economic damage, claiming that the use of less expensive alcohol alternatives has hurt small agave farmers in Mexico by lowering the market price of agave.

Diageo has denied the allegations and stated that both brands comply with U.S. and Mexican regulatory standards. The company also maintains that the tequilas are certified by Mexico’s tequila regulatory body, the Consejo Regulador del Tequila (CRT).