Federal agencies such as the US Forest Service, Bureau of Land Management, and National Parks Service have historically managed public lands, but Indigenous nations were excluded from decision-making processes. To address this history of dispossession and exclusion, federal agencies are beginning to engage with Tribal entities as equal partners in land management decisions. This paper examines the concept of Co-management as an approach to meaningfully engage with Tribes, emphasizing principles such as recognition of tribes as sovereign governments, incorporation of federal government trust responsibilities to tribes, and meaningful integration of tribes in decision-making processes. Using the principles laid out in the foundational work of Tribal Co-management by Ed Goodman, this thesis evaluates two case studies of Tribal Co-management in the American Southwest: Bears Ears (BENM) and Baaj Nwaavjo I’tah Kukveni Ancestral Footprints of the Grand Canyon (BNIKNM) National Monuments. These case studies highlight successful Tribal-led proposals for National Monument designation and subsequent Co-management models, setting important precedents for the future of conservation. This paper explores how Co-management is positioned to repair the broken relationship between federal land management agencies and Tribal entities and simultaneously repair the harmful legacy of public lands management. By examining specific strategies used by Tribes at BENM and BNIKNM to achieve successes in Co-management, this paper contributes to the larger conversation on strategies for achieving Indigenous Environmental Justice.