Interior Secretary Ryan Zinke will soon send recommendations to President Donald Trump that could do one of three things to the Katahdin Woods and Waters National Monument: revoke, diminish, or retain its designation as a national monument. Only one of those options, however, is legally and equitably permissible — the monument status must be retained.

Designated in August 2016 under the Antiquities Act, the Katahdin Woods and Waters National Monument may be new, but the scientific and historical significance of the area is well known to Mainers, from the East Branch of the Penobscot River, which has been relied on for centuries by Wabanaki people, to routes traveled by Theodore Roosevelt and Henry David Thoreau.

These woods are home to pristine watersheds, rare plant species, stunning views of Katahdin, and wildlife from black bears to moose to Canadian lynx. The geology, ecology and history of the area can, and should, be protected through national monument status. Further, this designation was made after years of meetings and public input. Indeed, the reason hunting and snowmobiling are allowed in parts of the monument is because of that public input. (These activities are typically prohibited in national parks.)

Let’s start with the most drastic purported “option” — revocation. The president lacks the legal authority to exercise this option because only Congress has the power to revoke monument designations. The Constitution plainly vests power over federal property with Congress. Through the Antiquities Act, Congress delegated a small slice of that property management power to the president — the power to declare national monuments and reserve land. That’s it. Congress did not give the president the power to undo such declarations or reservations. Congress retained that power for itself.

In the case of Katahdin Woods and Waters, the federal government also is constrained by the gift agreement made with the Maine family who donated the land. The documents formalizing the gift of the land specifically state that the donation was “for the purpose of establishing a national monument to be managed as unit of the National Park System.” If the federal government were to remove the monument designation, it would violate this express purpose as well as the intentions of the private landowners who donated their property in order to establish a public space for all citizens to enjoy.

Even if it were legally permissible, revocation of the monument status would erode trust in the federal government and chill similar donations in the future. Such an action would also financially harm local residents who, in reliance on the government’s monument designation, have invested in their own private businesses. In sum, it would be both illegal and inequitable for the executive branch to revoke the existence of the monument.

As for the diminishment “option,” which would reduce the size of the monument, lift certain restrictions on activities permitted there or both: this too would overstep the president’s authority. It is the job of the courts — not the president or the Department of the Interior — to determine whether a particular monument has been properly designated. Similarly, neither the president nor the interior secretary can lift restrictions on the land that are in place to protect the objects of historic or scientific interest. Indeed, the opposite is true: The Antiquities Act requires the Department of the Interior manage national monuments with such protections.

Of Secretary Zinke’s three purported options, only one is legally permissible: to retain Katahdin Woods and Waters as properly designated. This outcome complies with the Antiquities Act, upholds the agreement between the former landowners and the government, and respects the investment that people of this state have already made in and around the monument.

Finally, there has been some suggestion that removing the monument designation would somehow give the land back to Mainers and take it away from the federal government. This is absurd. The land now belongs to the federal government, regardless of whether it is designated as a monument. Removing that designation would give absolutely no power to the state of Maine or local residents.

The land previously belonged to Mainers who desired to create a monument. As private landowners in our state, they made a generous gift. They could very well have retained the land as their “sole and despotic dominion,” excluding all who now want to access it. They would have been within their rights to ban all hunting, snowmobiling and timber harvesting from this property.

We are all better off because of the choice our fellow citizens made to give their land to all of us, for our enjoyment and that of generations to come, and for the purpose of protecting our shared heritage.

Anthony Moffa is a visiting professor of law and Sarah Schindler is a professor of law and Glassman Faculty Research Scholar at the University of Maine School of Law in Portland. They specialize in environmental, land use and property law.