The people of the Tsilhqot’in Nation have, and continue to, govern their lands according to dechen ts'edilhtan, the laws of their ancestors. Through their history, their control over their lands and waters have faced opposition from outside forces which include neighbouring nations and settler governments into the colonial present. Over time, their laws have remained strong and deeply internalized, and yet have been exercised to maintain their contested control up to the present. One profound moment when Tsilhqot’in laws became apparent to outsiders was when laws relating to access to the nen (Tsilhqot’in land) effectively proved the Tsilhqot’in Nation’s claim of Aboriginal title over a portion of their territory at Canadian law in 2014. This dissertation provides a deep analysis of dechen ts'edilhtan as it applies specifically to use of and access to surface water in the Tsilhqot’in nen. The purpose is two-fold. First, to continue the ongoing work of understanding and articulating Tsilhqot’in law. Second, to facilitate the identification of possible methods through which ancestral laws may engage Canadian legal and political systems for the benefit of Tsilhqot’in people, and indeed, all Canadians. / Graduate / 2023-01-17