Garnering international support has been a strategy for many Environmental Justice (EJ) movements in the Global South. Due to the economic dependency of Southern governments on multilateral funding institutions and international trade, many Southern EJ movements utilized the “boomerang” effect (Keck & Sikkink, 1998). The process entails support by international allies in pressuring Northern governments, which in turn influence international norms and institutions, forcing the Southern domestic governments to comply. I analyze several classic Southern EJ movements which used the “boomerang” effect to better understand the operationalization. These include the Rubber Tappers’ movement in Brazil, the Narmada anti-dam movement in India, the Zapatista uprising in Mexico, and the Ogoni movement in Nigeria. The results show that not all Southern EJ movements could achieve the intended “boomerang” effect, even when they received widespread international support. Thus, internationalization is insufficient on its own, and is usually only one of the many protest strategies deployed by Southern movements. Understanding these processes provide valuable lessons on global EJ movement strategy. The Northern movements could learn from their Southern counterparts, including on how to perform better supporting roles.