Studies show that liberalizing governments include social and environmental clauses in trade agreements to gain pro-trade support from activists. However, these studies do not address how the government makes issue linkage credible to activists, who understand that the government has weak incentives to enforce such linkages once the agreement is ratified. How do liberalizing governments make issue linkage credible to activists despite the commitment problem? Focusing on U.S. government decisions regarding environmental clauses in trade agreements, I argue that a liberalizing government uses international treaties to mitigate activists’ fears of defection. By recognizing environmental international organizations’ authority in trade agreements, the government can mitigate activists’ fear of defection and increase their support for trade agreements. Using original data, I find that the government recognized environmental treaties with more ties to U.S.-based activists in designing environmental clauses in trade agreements from 2000 to 2016. Based on a comparative case study, I also show that activists with ties to recognized treaties supported issue linkage whereas those without ties to the treaties joined forces with anti-trade groups.