Of all America’s legal marijuana dealers, MedMen Enterprises has crafted its shops and packaging to the highest gloss. Not so much its investor communiqués. Earlier this week, the Canada-listed American cannabis chain (ticker: MMEN.Canada or MMNFF.OTC) issued a long statement explaining that a publicity campaign had gone awry.

MedMen said that it had hired an investor-relations firm by the name of “Wining Media LLC” to “drive the awareness of the Company, its business and its securities,” through ads on Google and Yahoo Finance,...