Abstract: This article examines how different federal configurations can shape Indigenous autonomy across three cases: The United States, Canada, and Australia. While federations might seem better equipped than unitary states to share sovereignty with Indigenous peoples, they often entrench settler authority by internalizing Indigenous affairs, thereby limiting Indigenous self-government. Through a comparative historical analysis, this study shows that Indigenous autonomy is enhanced when settler governments externalize Indigenous affairs—treating them as nation-to-nation relationships through treaties or constitutional agreements. The article identifies two mechanisms that support such externalization: aligning Indigenous affairs with settler powers over foreign relations and separating them from settler control over land and resources. Drawing on constitutional and jurisdictional history, the study offers a novel framework for understanding how federal systems can either constrain or support Indigenous self-determination in the US, Canada, and Australia, highlighting the promise of treaty federalism as a path toward greater Indigenous jurisdiction and autonomy.