Do flexibility provisions in international agreements—clauses allowing for legal suspension of concessions without abrogating the treaty—promote cooperation? Recent work emphasizes that provisions for relaxing treaty commitments can ironically make states more likely to form agreements and make deeper concessions when doing so. This argument has particularly been applied to the global trade regime, the General Agreement on Tariffs and Trade (GATT) and its successor, the World Trade Organization (WTO). Yet the field has not produced much evidence bearing on this claim. Our article applies this claim to the global trade regime and its chief flexibility provision, antidumping. In contrast to prior work, this article explicitly models the endogeneity and selection processes envisioned by the theory. We find that states joining the WTO are more likely to adopt domestic antidumping mechanisms. Likewise, corrected for endogeneity, states able to take advantage of the regime's principal flexibility provision, by having a domestic antidumping mechanism in place, are significantly more likely to (1) join the WTO, (2) agree to more tightly binding tariff commitments, and (3) implement lower applied tariffs as well.