It also authorizes the President to reserve parcels of land surrounding these objects, but limits the size of such reservations to "the smallest area compatible with the proper care and management of the objects to be protected." Since its enactment, Presidents have used the Antiquities Act to establish 158 national monuments, reserving millions of acres of land in the process, and to modify existing monuments more than 90 times. Though most monument proclamations have been uncontroversial, some have precipitated corrective legislation and litigation. Attempts to undo proclamations through litigation have been less successful, as courts have uniformly upheld challenged proclamations through a broad interpretation of the Antiquities Act. Finally, the report discusses the current litigation involving President Trump's proclamations diminishing the Grand Staircase-Escalante and Bears Ears monuments, with a focus on the parties' arguments addressing whether the Antiquities Act authorizes the President to diminish a national monument. The second section—the core of the act—authorizes the President "in his discretion" "to declare by public proclamation historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest that are situated upon the lands owned or controlled by the Government of the United States to be national monuments." No President has purported to abolish a national monument, but past Presidents have reduced the size of monuments on 18 separate occasions. The Senate Committee on Public Lands and Surveys went further, and concluded that the Jackson Hole proclamation "disregarded" the Antiquities Act's requirement that reserved lands be "confined to the smallest area" necessary for preservation. This case involved a challenge to President Clinton's designation of the Grand Staircase-Escalante monument, with the plaintiffs taking the view that the President exceeded his authority under the Antiquities Act by "fail[ing] to designate the requisite objects of historic or scientific value" and "not limit[ing] the size of the monument to the 'smallest area' necessary to preserve the objects." This was the first time since President Kennedy that a President has diminished a national monument. The plaintiffs contend that the President's authority under the act is limited to the express grants of authority in the text itself, namely, the power to "declare" monuments and to "reserve" surrounding lands—neither of which includes or implies the distinct power to diminish or revoke a monument. That law expressly authorized the President to "revoke, modify, or suspend" existing forest reservations in order to "remove any doubt" regarding the President's authority to do so. By contrast, the United States argues that the Antiquities Act does authorize the President to modify a previously established monument. Past Executive and Legislative Action

Noting that historical practice may inform a court's understanding of executive power, the United States argues that the long-standing practice of executive monument modification and congressional acquiescence in this practice shows that the President has authority under the Antiquities Act to modify existing monuments. Second, in opinions from 1935 and 1947, the Department of the Interior argued for presidential modification authority based on the language in the Antiquities Act requiring that lands reserved be "the smallest area compatible" for the preservation of the designated objects. The plaintiffs note that even during the time when several Presidents were reducing monuments, various departments within the executive branch issued opinions concluding that the President does not have implied authority to undo a reservation of land. Finally, the plaintiffs rely on the enactment of the Federal Land Policy and Management Act of 1976 (FLPMA) to show that the President lacks authority to modify national monuments. While acknowledging that FLPMA's prohibition is directed to the "Secretary"—not the President—the plaintiffs point to the House report accompanying the legislation, which stated that FLPMA "reserve[s] to the Congress the authority to modify and revoke withdrawals for national monuments created under the Antiquities Act" —suggesting an intent to consolidate all withdrawal authority in Congress. Some plaintiffs also note that President Trump's proclamations not only reduced the amount of land reserved for these monuments, but also removed certain objects from these monuments. However, though the President's authority to diminish monuments may reasonably be questioned, it appears clear that Congress has authority to codify or repeal a presidential proclamation. Other Members of Congress have proposed amending the Antiquities Act to limit the President's authority to declare national monuments and to bar the President from diminishing existing monuments, except in specified circumstances.
Summary
The Antiquities Act authorizes the President to declare, by public proclamation, historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest situated on federal lands as national monuments. The act also authorizes the President to reserve parcels of land surrounding the objects of historic or scientific interest, but requires that the amount of land reserved be confined to the smallest area compatible with the proper care and management of the objects to be protected. Since its enactment in 1906, Presidents have used the Antiquities Act to establish 158 monuments, reserving millions of acres of land in the process. Presidents have also modified existing monuments, whether by increasing or decreasing their size (or both), on more than 90 occasions.
Though most monument proclamations have been uncontroversial, some have spurred corrective legislative action and litigation. Congress has twice imposed geographic limitations on the President's authority under the Antiquities Act in response to proclamations reserving millions of acres of land in Wyoming and Alaska. Litigants have also challenged the President's authority to establish certain monuments, disputing whether the historic or scientific objects selected for preservation were encompassed by the act, as well as whether the amount of land reserved exceeded the smallest area necessary for the objects' preservation. Courts, however, have uniformly rejected these challenges and adopted a broad interpretation of the President's authority under the Antiquities Act.
No President has purported to revoke a national monument, but past Presidents have reduced the size of existing monuments on 18 occasions. In 2017, President Trump issued proclamations reducing the size of the Grand Staircase-Escalante National Monument and the Bears Ears National Monument. Various groups have sued to block these proclamations, arguing that the President exceeded his authority under the Antiquities Act. Because none of the prior proclamations diminishing monuments was challenged in court, these lawsuits offer the first opportunity for a court to decide whether the act empowers the President to diminish a national monument.
Those challenging President Trump's proclamations argue that the Antiquities Act's authorization for the President to "declare" national monuments and "reserve" surrounding lands does not include the distinct power to revoke or diminish an existing monument. They underscore this point by noting that, unlike the Antiquities Act, several contemporaneous public land laws expressly authorized the President to undo a prior reservation of land. The plaintiffs also highlight a number of 19th and early 20th century legal opinions from the executive branch concluding that the President lacks authority to undo a reservation of land absent express statutory authorization. Finally, the plaintiffs argue that the Federal Land Policy and Management Act of 1976 (FLPMA)—which prohibited the Secretary of the Interior from modifying or revoking a national monument established under the Antiquities Act—demonstrates Congress's intent to consolidate modification power in the legislature.
By contrast, the United States argues that the requirement that reserved land be "the smallest area compatible" with the preservation of the designated objects empowers the President to reduce the size of a monument when he determines that more land was reserved than necessary. The United States also contends that the Executive has implied authority to revisit prior discretionary decisions. Further, the United States argues that the President's authority to diminish monuments is confirmed by the 18 times past Presidents have done so and by several executive branch legal opinions that support this conclusion. Finally, the United States argues that FLPMA is irrelevant because that law prohibits the Secretary of the Interior, not the President, from diminishing monuments.
While the President's authority to diminish a national monument has been questioned, there appears to be no dispute that Congress has authority to do so, a power it has exercised before. Several Members of Congress have introduced legislation either codifying or reversing President Trump's proclamations or placing limits on the President's authority under the Antiquities Act going forward.