In July 2016, we concluded work for the Washington law firm, Garvey, Schubert, and Barer in their continuing efforts seeking protection of Manitoba waters in respect of the Northwest Area Water Supply (NAWS) project proposed by North Dakota, the US Bureau of Reclamation and the US Army Corps of Engineers. Our efforts, building on our extensive technical work that began in 1997, supported formal filings in US Federal court seeking denial of (or constraints upon) the NAWS project. The NAWS project could allow invasive species to pass into the Red River, flowing north to Lake Winnipeg, where they could impair Indigenous Peoples’, First Nations’, recreational, commercial, and domestic fisheries. We learned the outcome of all this work in August 2017. The Federal judge concluded that because of Manitoba’s repeated, scientific, evidence-based and legal arguments of insufficient analysis, the US Bureau had finally done sufficiently comprehensive impact-assessment work (the deficiencies outlined in great part through MLi3’s technical work) that US federal statutory requirements had, finally, been met. The judge held that there were many residual concerns for Manitoba’s interests. Nonetheless, she ruled against Manitoba, stating that the residual issues were political and policy, not legal, and hence not resolvable through the judge’s authority or discretion. MLi3’s efforts were an important contribution to landmark legal decisions defining the appropriate level of analytical care required in cases of proposed transboundary water-transfer projects.