In 1994, the provincial government of Quebec announced the abandonment of the Grande Baleine hydroelectric megaproject. Many reasons were given: decreasing demand, drop in the foreign market, pressure from Native and ecological lobby groups. To analyse this phenomenon, this paper examines the Judge Malouf's decision of 1973, that was overturned by the Court of Appeal and followed, in 1975, by the Convention de la Baie James et du Nord québécois. Still in effect, this treaty is now being contested. However, to understand its full meaning, we have to consider the spirit and the letter of the Convention instead of the attacks against it. Then the premises of a political encounter between First Nations people and Quebecers can be discovered.