Tribal nations have a complicated relationship with the 1973 Endangered Species Act. Tribal governments have used the ESA on behalf of imperiled, culturally important species, litigating over dams that block salmon migration and securing funding to reintroduce protected species on their lands. But beyond Alaskan Native subsistence hunting rights, the law does not acknowledge tribal sovereignty. How, or even if, it affects treaty hunting rights and other aspects of sovereignty remains a disputed question. The Endangered Species Act can be “both sword and shield for tribes,” said Monte Mills, director of the Native American Law Center at the University of Washington.