Four aid workers were convicted Friday on charges connected to their efforts to leave food and water for migrants in an Arizona wildlife refuge along the U.S.-Mexico border.

The volunteers, who are members of the faith-based humanitarian aid group No More Deaths, were caught on Aug. 13, 2017, by a Federal Wildlife officer as they left water jugs, beans and other supplies for migrants in Cabeza Prieta National Wildlife Refuge, which shares a 50-mile border with Mexico. No More Deaths claims that 155 migrants have died in the refuge since 2001, and that the organization aims to save lives by providing basic supplies.

The judge, United States Magistrate Bernardo P. Velasco, ruled that three of the volunteers – Oona Holcomb, Madeline Huse and Zaachila Orozco-McCormick – were convicted of entering a national wildlife refuge without a permit and abandoning personal property or possessions. A fourth volunteer, Natalie Hoffman, was convicted on an additional charge of operating a motor vehicle in a wilderness area. Each of the volunteers faces up to six months in prison.

The decision is the first conviction against humanitarian aid volunteers in a decade, the Associated Press reported.

Velasco wrote in his verdict that the women had failed to get permits for expanded access to the wildlife refuge, had gone off the roads where they are allowed to travel and left behind their belongings. The verdict said that their actions “[erode] the national decision to maintain the refuge in its pristine nature.”

No More Deaths responded to Velasco’s verdict by claiming that the decision is part of a larger crisis of conscience in the U.S. Catherine Gaffney, a volunteer for the organization, said that the four volunteers were driven by moral principles.

“This verdict challenges not only No More Deaths volunteers, but people of conscience throughout the country. If giving water to someone dying of thirst is illegal, what humanity is left in the law of this country?” Gaffney said.

Five other humanitarian aid volunteers are also facing trial later this winter on similar charges, the nonprofit said.

The judge rejected several defenses the volunteers used to explain their actions, including a defense that they had been acting on their “moral, ethical and spiritual belief to help other people in need.”

He also rejected the claim that an Assistant United States Attorney had deliberately misled the organization by telling them that the Department of Justice did not plan to prosecute aid workers.

Velasco went on to chastise the organization for misleading the volunteers about the legal risks they faced.

“Each one acted on the mistaken belief that the worst that could happen was that they could be banned, debarred… or fined,” he wrote in his verdict. “No one in charge of No More Deaths ever informed them that their conduct could be prosecuted as a criminal offense nor did any of the Defendants make any independent inquiry into the legality or consequences of their activities.”

In response to the verdict, No More Deaths announced that it would hold a vigil outside of Eloy Detention Center in Arizona on Saturday night.

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