A Minnesota judge dropped charges against a trio of climate change activists, saying prosecutors failed to prove that they had actually caused any damage.

Defendants Emily Johnston and Annette Klapstein admitted that they had turned the emergency shut-off valves on oil pipelines owned by Enbridge which carried Canadian Tar Sands Oil about 335 kilometers northwest of Minneapolis on 11 October 2016.  The third defendant, Ben Joldersma, called in a warning to Enbridge.  This was all part of a broader plan by the group Climate Direct Action to shut five tar sands pipelines from Canada to the US. 

The prosecution had rested its case and the judge issued the sudden ruling, ending the trial.  This cut off the activists' attorney from commencing a novel "necessity defense" that would have posited that the defendants' actions were not only morally right, but crucial for the survival of the human race on earth. 

The "necessity defense" tactic has met with mixed success:  Earlier this year, a judge in Massachusetts cleared 13 defendants who shut down a gas pipeline.  Other activists in less progressive states were convicted and tossed in jail.

The Minnesota defendants are frustrated that they did not get to put climate change itself on trial by presenting evidence that tar sands crude is much more dangerous than pumped oil because it generated more carbon dioxide.

"I'm very relieved the state of Minnesota acknowledged that we did no damage and intended to do no damage," said Emily Johnston, "I also admit that I am disappointed that we did not get to put on the trial that we hoped for."

Prosecutors declined to comment.