A recent legal judgment could force Greenpeace to pay $667 million in defamation and vandalism-related damages, from the 2016 protests against the Dakota Access Pipeline leading environmentalists to worry that the ruling could have a chilling effect on climate activism. Michael Gerrard, professor of law at Columbia Law School and the founder and faculty director of the Sabin Center for Climate Change Law, shares his legal analysis of the case, and what it could mean for the environment.