On October 11, 2016, five climate activists simultaneously closed the emergency valves on the five pipelines carrying Canadian tar-sands oil into the United States — Ken Ward, Emily Johnston, Annette Klapstein, Leonard Higgins, and Michael Foster, with their support crews — then waited to be arrested, in order to put the climate emergency itself on trial. Foster served six months in North Dakota; the others faced years-long maximums across four states.

Their cases turned the necessity defense into the movement's courtroom: a Minnesota court allowed expert climate testimony before acquitting Johnston and Klapstein outright, and Ward's Washington juries refused to convict on the felony. The valve turners — grandparents, retired attorneys, a pediatrician — normalized the proposition their trials argued: that in a physical emergency the law's presumptions reverse.