Since 2000, Allisun has provided legal advice to First Nations on a variety of issues, including the Crown’s Legal obligation to consult, breach of fiduciary duty, Treaty and Aboriginal rights, and various Indian Act and Governance matters. She has appeared at all levels of court in British Columbia, Alberta and Saskatchewan, and has ben involved in litigating a number of leading cases, including Mikisew Cree Frist Nation v. Canada (Minister of Canadian Heritage) in the Supreme Court of Canada and West Moberly First Nations et al v. British Columbia et al (the Western Boundary of Treaty 8 case) in the Supreme Court of British Columbia. She has intervened in numerous appellate level cases such as Whitefish v. Canada (Attorney General) in the Ontario Court of Appeal, and Taku River Tlingit First Nation v. British Columbia and Behn v. Moulton Contracting in the Supreme Court of Canada. She also litigates in the Specific Claims Tribunal.

Allisun’s experience in regulatory and environmental law includes providing legal and strategic advice to First Nations on consultation and assisting them with their participation in environmental assessments and intervention in other regulatory processes for major projects. She has appeared before federal and provincial regulatory boards in both British Columbia and Alberta and represented Treaty 8 First Nations in British Columbia through the environmental assessment process for the Site C Dam. She was also a member of the legal team that represented the British Columbia Treaty 8 First Nations in the Site C judicial reviews and appeals.

Allisun is also trained in interest-based negotiation and works collaboratively with her clients to build effective negotiation teams. She has negotiated resource management and consultation agreements with governments and impact benefit agreements with project proponents. She also represents First Nations in the submission and negotiation of claims in the federal Specific Claims process and in self-government negotiations with the federal government. Allisun also negotiates commercial agreements on behalf of First Nations and her involvement in First Nations community development initiatives has included the development and implementation of First Nations trusts, the design and facilitation of reserve land selection processes, the coordination of traditional use studies, and applications under Canada’s Additions-to-Reserve policy.

Allisun is recognized as a leading practitioner in Indigenous law by the Canadian Legal Lexpert® Directory and was a finalist for the 2017 Women in Law Leadership Award in the category of Leadership in the Profession (Private Practice).