Abstract: Although the international community has addressed whether environmental harm violates human rights norms, only recently has it asked whether international organizations must implement those norms. That changed when Greenland posited that the International Whaling Commission (IWC) has a duty to implement aboriginal subsistence whaling (ASW) in light of customary international human rights norms, including the rights to cultural identity and resources. This article explains why international organizations have an obligation to implement customary international human rights law. Implementation, however, may be challenging because the content of some rights is not clear. In addition, these rights are not absolute. Actions may interfere with human rights provided they can be reasonably and objectively justified, as the United Nations Human Rights Committee has concluded, or are necessary, legitimate, and proportional, as the Inter-American Court of Human Rights has stated. The article concludes that the IWC’s ASW management regime interferes with certain customary international human rights, but that it can be reasonably and objectively justified or is necessary, legitimate, and proportional. Nonetheless, the IWC could strengthen implementation of human rights by, for example, clearly articulating criteria for preparing and evaluating “need statements”—the statements submitted to support an ASW quota.