This may not be the real estate deal many were expecting under the Trump administration.

According to The Guardian, a rule change instituted by Congress will “ease the path” to selling million of acres of federal land to private interests.

The process wouldn’t be immediate: The rule change would make it easier to transfer the land to the states. But that seemingly slight shift opens some distinct possibilities, such as releasing millions of acres from federal stewardship, including some directly adjacent to national parks (proposed uranium mining near the Grand Canyon last year led activists to push for a Greater Grand Canyon Heritage National Monument). Doing so would eliminate mixed-use requirements, limit public access, and potentially give states the power to turn over large tracts of land to energy or property development.

What’s crucial to note here is that the federal property at stake—overseen by the Bureau of Land Management (BLM), National Forests, and Federal Wildlife Refuges—contributes an estimated 6.1 billion jobs and an ongoing $646 billion a year in economic stimulus, according to an Outdoor Industry Association study.

The federal property at stake contributes an estimated 6.1 billion jobs and an ongoing $646 billion a year in economic stimulus.

That federal land is the government’s second largest income source after taxes, according to the Outdoor Alliance. And the BLM alone made $2 billion in royalty revenue annually from leasing federal land for oil and gas production, logging, and other industrial uses.

How did the act come to pass? The new Congressional budget rules put in place January 2 created a loophole, with language that denies that federal land has any value at all. That rule then allows Congress to circumvent a law stating that a transfer of federal land not decrease federal revenue or add to the federal debt. Basically, if land value is “worthless,” it won’t impact the bottom budget line.

Alan Rowsome, senior director of government relations at The Wilderness Society, spoke to the The Guardian, saying, “This is the worst Congress for public lands ever.” Rowsome projects a few obvious federally-owned places that would benefit commercial interests, if transferred: areas adjacent to the Grand Canyon National Park in Arizona and Minnesota’s Boundary Waters Canoe Area Wilderness, due to their mineral wealth, and the Arctic National Wildlife Refuge, oil-rich and potentially a target for drilling.

This move is, of course, not totally unprecedented: President Reagan was a champion of giving federal land to the states, and many legislators have recently pushed similar proposals, including Montana Congressman Ryan Zinke, Trump’s nominee for Secretary of the Interior.