Serge Simon, left, Grand Chief of Kanesatake, Ghislain Picard, Chief of the Assembly of FirstNations of Quebec and Labrador listen to drummers during a treaty signing ceremony. Paul Chiasson/Canadian Press
Across North America, more than 100 indigenous leaders have signed a treaty against Alberta's tar sands, effectively putting those who want to build oil sands pipelines—including Prime Minister Justin Trudeau—on notice.