The environmental group is being sued for $300 million in North Dakota by a pipeline company in a case that has become a flash point in the debate over free speech.

The trial in North Dakota that observers are describing as a key free speech rights case has begun. Energy Transfer, a Texas-based company and the operator of the Dakota Access Pipeline, is suing Greenpeace for alleged defamation and what their lawyers describe as a “campaign of violence.”

The company behind the controversial Dakota Access Pipeline is suing Greenpeace for at least $300 million for damages the oil pipeline company says it suffered from protests in 2016 and 2017.