AJO, Ariz. — “A wilderness, in contrast with those areas where man and his works dominate the landscape, is hereby recognized as an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain.”

So begins Section 2 (c) of the Wilderness Act of 1964, a federal law that today protects some 110 million acres in the United States.

It is also, today, being used to underpin a criminal complaint that has sent chills through the immigrant rights community.

Last year, federal prosecutors charged a group of activists with illegally entering the Cabeza Prieta National Wildlife Refuge, a rugged area in southern Arizona that spans some 800,000 acres of sepia-toned desert and pleated mountains along the border with Mexico.

Their crime: entering without permits to search for migrants who went missing after crossing into the United States illegally and then leaving behind water and other goods when they could not find them.

Four people were convicted this month, and more face trial.

Although not the first time the government has gone after the activists, the breadth of the campaign against them, and the use of the Wilderness Act, appears to be a first.

Ordinarily, people caught wandering the refuge without a permit might be sent off with a warning or perhaps a summons. The Trump administration opted for the most severe approach.

“The cases are on their surface about wilderness, but I think sitting in the courtroom and watching the trial really laid bare the fact that it’s not just about wilderness,” said Parker Deighan, one of the volunteers awaiting trial on a misdemeanor charge in the case. “It is about targeting humanitarian aid and targeting care for folks who cross the border.”

In convicting the activists, a federal judge said their actions had eroded “the national decision to maintain the refuge in its pristine nature.” And “pristine” is a word that could be easily applied to much of the border area. Tracts of ridged desert populated by barrel cactus and giant saguaros that hug the skyline are untouched reservation land for 75 miles of the border.

And yet a wall could be coming. This despite the fact that one already exists.

The government’s action against the activists, whatever the legal merit, raises broader questions along the border, in particular here, where Arizona abuts its Mexican counterpart, Sonora.

Among them: Who exactly owns the land and gets to say what can or cannot be done to it? Who can make permanent man’s touch on the wilderness, and who suffers for it?

A short drive from Cabeza Prieta lie lands held by the people of the Tohono O’odham Nation. Here, the trammeling of the land has been done exclusively by the U.S. government in its campaign to seal off the dry edges of the United States.

“It is sort of a contradiction what they are doing here,” Verlon Jose, the Tohono O’odham Nation vice chairman, said on a recent tour through a section of the nearly 3 million acres granted to the tribe. “No one wants this wall, and they are saying they are going to build it anyways.”

The tribe has occupied the land for thousands of years, since before there were countries to separate with borders. Its land once stretched from central Arizona all the way down to Hermosillo, Mexico, but geopolitics forced a retreat.

Today, the tribe is fighting to preserve what’s left.

Jose and others are in a pitched battle to halt the construction of any more walls on their land, which is a wilderness in all but name, replete with saguaro forests, untamed brush and tracts of desert arroyo and washes that flood every spring.

The wall that exists now is a welded chain of X-barriers that form a straight line across the southern edge of Tohono O’odham land. To the side, a dirt road has been scratched out of the plains.

This was, to many on the reservation, already a sore point.

More than 2,000 members of the tribe are registered in Mexico. Graveyards sit across the fencing in place now, accessible through a few unmanned border gates exclusively for tribe members.

A new wall would upend nature entirely — from the unspoiled views across a landscape indifferent to borders to the animal life whose free passage between sides would end.

“It’s our backyard,” said Jose. “There’s not just the physical effect of a wall. It’s psychological and emotional as well.”

This article originally appeared in The New York Times.