On August 19, Monica Sud, a woman from California, filed a class action lawsuit against Costco Wholesale Corporation claiming that the retailer knowingly sold prawns produced by slave labor and never disclosed these practices to customers like herself who bought the products without knowing they were produced by illegal labor.

The suit, Sud v. Costco Wholesale Corporation et al, comes after reports of major US and UK retailers selling seafood products that were traced back to slave labor facilities in ships located near Thailand. Sud’s standing for the suit was that she is a Costco customer. If that survives a court challenge, customers of other outlets named in the report could file their own suits.

In 2014, The Guardian accused Walmart, Carrefour, Costco and Tesco of using slave labor, after a six month long investigation into the practices of Charoen Pokphand (CP) Foods, reportedly the world’s largest prawn farmer.

According to The Guardian report, CP Foods uses fish meal from so-called “ghost ships,” where workers are held captive with chains and threatened with violence and death in order to pressure them to produce. Some of those interviewed claimed workers were killed for not meeting management’s production demands. Many of the slaves on the ghost ships were migrants lured by promises of work and a better life.

Sud’s class action suit demands that Costco stop selling prawns unless the company labels them a product of slave labor — something that would likely hurt sales. The intent of the suit appears to be to force Costco to follow through on the company’s promise to stop using slave labor.

Costco responded to the suit by saying the company would “continue to work with various stakeholders (including the Thai government, other retailers, and Thai industry) to address the issues that have surfaced.” The extent to which Costco is working with various stakeholders to stop selling food produced by slave labor is not altogether clear.

Costco also recommended, in general terms, that customers return items they were dissatisfied with.