When Emily Johnston shut the emergency valve on a pipeline in Minnesota carrying tar sands oil from Canada she hoped she was making a difference. It turns out she was making history.

In October 2016, Johnston and four other activists nicknamed the Valve Turners briefly shut down 15 percent of America’s oil supply to call attention to climate change. The Valve Turners called the pipeline companies to alert them, live-streamed shutoffs, and peacefully awaited their arrests in Minnesota, Washington, North Dakota, and Montana.

“I signed on for this, knowing I could go to prison, because of my increasing awareness of how dire the situation is,” says Johnston. “Even before the election it was clear the legal and political system needed some kind of shock.”

Johnston, along with fellow Valve Turner Annette Klapstein, and their video and support team, go on trial in January. They will likely be the first defendants in the United States to use the “necessity defense” for environmental reasons which allows defendants to argue that they committed a crime to prevent a greater harm from occurring — in this case the destruction civilization.

This was part of the Valve Turners’ plan all along, to extend their call to arms beyond the immediate impact of the event itself.

“The Valve Turners was visually dramatic and a high legal risk so we thought it might get the attention we need and then we could leverage that attention,” Johnston said.

Johnson’s partners in crime had tried persuading the courts to let them use this defense without success. Ken Ward, Michael Foster and Leonard Higgins were found guilty in Washington, North Dakota and Montana, respectively, after cutting padlocks to get to the valves. Ward was convicted of second-degree burglary and sentenced to perform community service; Foster was convicted of felony criminal mischief after a prosecutor compared him to the Unabomber and argued that acquitting him would lead down a slippery slope to Sharia law. Foster faces two decades in prison during his sentencing in January. Higgins was found guilty of felony criminal mischief and faces up to 10 years in prison.

“We knew the odds were quite slender but by doing this in four different states we had four separate chances,” Johnston says.

At the trial, the Valve Turners’ lawyers will bring forth expert witnesses, likely including the two leading voices on climate change: Dr. James Hansen, the former head of NASA’s Goddard Institute for Space Studies, and activist Bill McKibben, author of The End of Nature. Johnston believes their testimony will not only sway the jury it will also attract more high-profile media attention to the cause.

McKibben sees the necessity defense as part of a new wave of “creative resistance.”

“By far, the best thing of the past year has been watching people flock to the airport to try to protect immigrants and NFL players turn playing fields into sites for political reckoning,” he told The Daily Beast.

The Valve Turners aren’t the first to put forth the necessity defense for an environmental direct action though. Tim DeChristopher’s effort to use it was rejected after he was charged over disrupting a government auction in 2008 by bidding on oil and gas land leases for which he had no intention of paying. DeChristopher successfully prevented the sale but without the necessity defense he was found guilty and spent 21 months in prison.

Since then, the tactic has come closer to working. A judge approved it in 2014 after Ward and Jay O’Hara used a lobster boat to blockade 40,000 tons of coal from being delivered to a generating station in Massachusetts. However, a sympathetic prosecutor dropped the charges and even pledged to join the cause.

The defense was initially allowed in the “Delta Five” trial last year, involving an oil train blockade in Washington. But the judge reversed course before jury deliberations, declaring that defense lawyers had not sufficiently proven a lack of legal alternatives for resolving the situation, which is essential for the necessity defense.

In addition to the Valve Turners trial in Minnesota, the necessity defense has also been allowed a separate case for next year, this one involving the blockading of an oil train in Washington.

While environmentalists take Democrats to task for climate change actions ranging from timid to harmful, they say the stakes are far higher with climate change denier Donald Trump in the White House while Republicans who are equally dangerous on environmental issues control Congress.

“Trump ran on a platform of ruthlessness...and got stronger by displaying cruelty,” says DeChristopher, who said the administration could be a game changer for the necessity defense,

Ward said the necessity defense will start winning because “things are going to get worse and the more freaked out people become the more judges and juries are going to let people off.”

A jury verdict would carry more weight with the public than the opinions of activists, De Christopher believes, and bring to light how serious the crisis is.

McKibben agrees.

“People in our society haven't often sat still for a few hours and thought about the implications of climate change in that way,” he says of prospective jurors. “So if they do, suddenly what seemed at first glance to them as odd and alarming [the Valve Turners’ actions] may suddenly appear to them in a very different light.”

But the addition of the necessity defense to the activists’ arsenal raises important questions about what can be justified as necessary, and how far environmentalists may be willing to go to test the limits.

If Americans are persuaded that the only way to save the planet is to break the law then it raises the question of whether jurors might be willing to accept actions beyond carefully planned, safety-first protests like the one by the Valve Turners.

“What’s justified is a hard question,” says Travis Nichols, Greenpeace USA’s media director. “I don’t believe the peaceful protest has been exhausted. Things are dire but we can still stop the worst effects and the future has not been foreclosed upon.”

Indeed, less than a month after the Valve Turners event, Ruby Montoya and Jessica Reznicek of Iowa began their own pipeline sabotage campaign, setting fire to heavy machinery and cutting through or burning empty pipeline valves and electrical units. They later publicly claimed responsibility, endorsing the safe use of arson, hoping to inspire others to take action.

“The government is creating an atmosphere of frustration and anger that could indeed lead to [more destructive] attacks,” says Paul Watson, founder of Sea Shepherd. “It's almost inevitable the way this is going.”

Radical environmentalism is nothing new, nor is the debate over how far to go for the cause.

The modern movement started shortly after Edward Abbey published his 1975 novel The Monkey Wrench Gang , which made the case for sabotage in defense of the environment. Two years later, Watson was forced out of Greenpeace in part because he wanted to pursue “aggressive non-violence.”

Others went further, like like Earth Liberation Front and Earth First: they drove spikes into trees to disrupt logging and set fire to lumber companies, an SUV dealership, and a college library. (There were a few injuries and some activists publicly regretted using arson.)

Meanwhile, Watson founded Sea Shepherd and the group gained notoriety by ramming and even sinking ships to stop illegal whaling. Damaging property is not a violent crime to Watson.

“If a poacher is about to shoot an elephant and you knock the gun out of his hand and break the gun, is that an act of violence? I look at it as an act of nonviolence.”

The current round of direct action protests reflects that split, although no one has gone as far as the Earth Liberation Front and Earth First extremists—yet.

When Ward and O’Hara planned their lobster boat blockade, they limited their efforts “because we wanted to be as lawful as possible.” Even with the Valve Turners, Ward was hesitant to cut padlocks. “It seemed incidental,” he says, “but it is a threshold step.” Once you break the law in the name of a cause, the discussion shifts to how many laws can and should be broken given the enormity of the stakes.

“I don't think we should ever do anything that has any real risk of injuring people or the environment,” Ward says.

If activists do resort to violence, the bad guys win, Greenpeace’s Nichols believes.

“That’s their dream scenario, the idea that peaceful protest has run its course and they can respond with disproportionate violence.” And if the activists lash out then the necessity defense loses potency.

“I doubt that right now something like blowing up a refinery would resonate with the public,” DeChristopher says. “If people thought, ‘No one is going to understand this even if we’re allowed to use the necessity defense’ then it might be good to reconsider their actions. That’s part of the brilliance of this system.”

Still, as climate change worsens, activists believe people will stretch the boundaries of direct action. DeChristopher says he’d even keep an open mind to applying the necessity defense to the sort of attacks perpetrated by ELF and Earth First in the previous generation if others tried it.

“We know there's going to be more sabotage in the climate movement, which is why it’s so important that we start actually making shifts in our society now,” he says. “People are not going to give up, whole generations are not just going to die quietly. If people continue to dismiss this existential threat to our civilization, we will continue to see escalating chaos to our society. There's no doubt about that.”