Government contractors and other big companies that do business overseas should pay close attention to a human trafficking case before the U.S. Court of Appeals for the Ninth Circuit.

If Cambodian villagers are able to revive claims of abuse against companies involved in a Thailand shrimp venture, contractors could endure lawsuits for the alleged trafficking and labor misconduct of companies in their supply chain with whom they had limited interaction just by ordering products from them.

The Cambodian plaintiffs traveled to Thailand to work at factories preparing shrimp and seafood—for export to U.S. customers like Walmart Inc. and Kroger Co....