A place of great natural beauty, popular among rock climbers and campers, a part of Tonto National Forest known as Oak Flat has been under federal protection from mining since 1955, by special order of President Eisenhower.

On the nearby San Carlos Apache reservation, many consider Oak Flat to be sacred, ancestral land – the home of one of their gods and the site of traditional Apache ceremonies.

But Oak Flat also sits on top of one of the world’s largest deposits of copper ore. Resolution Copper Mining, a subsidiary of British-Australian mining conglomerate Rio Tinto, has sought ownership of the land for a decade, lobbying Congress to enact special legislation on its behalf more than a dozen times since 2005.

Year after year the bills failed to pass. But in December, the legislation was was quietly passed into law as part of the 2015 National Defense Authorization Act, of the  Arizona Sen. John McCain, who has long championed the deal, said the land exchange would strengthen th US military since copper is the second-most-utilized mineral by the Department of Defense.

As part of the deal, Resolution Copper will swap roughly 7.8 square miles of land scattered across Arizona for roughly 3.8 square miles of Tonto National Forest, which includes Oak Flat. The new legislation will open up Oak Flat for copper mining.

But critics say the move allows the company to privatize the land and make an end run around critical environmental and cultural protections. What’s more Resolution Copper can’t promise that any of the copper produced by the mine will remain in the United States – which raises the question: How does this help national defense?