This article examines why the growing supply of farmed salmon certified by the Aquaculture Stewardship Council (ASC), a leading standard for responsibly farmed seafood, has been sold as conventional, unlabeled salmon in some countries. Two countries are examined: Norway, the world’s main producer of ASC-certified farmed salmon, and the United Kingdom, a longstanding demand-side market leader on eco-labels. The study finds that unresolved environmental challenges of salmon farming, combined with perceived weaknesses in the ASC salmon standard, have led not only non-governmental organizations but also several major retailers to view the ASC as not setting the bar high enough to enable salmon farming to be defined as “sustainable.” Consequently, many producers and retailers use ASC certification only on a business-to-business level and have not been incentivized to label salmon products as “responsibly farmed” in supermarkets and other consumer markets.