From Preservation Action:

Last week, the US Supreme Court refused to hear a pair of cases that could have limited presidential authority to establish new national monuments under the Antiquities Act. Review of two lawsuits were sought before the court challenging the expansion and management plans of the Cascade-Siskiyou National Monument in Oregon. A group of Republican lawmakers submitted an amicus brief in support of the lawsuits. 

While courts have long sided with Presidents, affirming their authority to designate new national monuments, challenges remain. Opponents of the Antiquities Act hope to bring another case to the Supreme Court, challenging President Biden's decision to redesignate Grand Staircase-Escalante National Monument and Bears Ears National Monument in Utah. In August, a federal judge upheld these designations, again affirming Presidential authority under the Antiquities Act. 

Additionally, current legislation being considered in the House and Senate would limit the effectiveness of the Antiquities Act and restrict the President's authority to establish future national monuments. The Congressional Oversight of the Antiquities Act (H.R. 5499, S. 2820) was considered as part of a House Natural Resources Federal Lands Subcommittee legislative hearing last month. 

The Antiquities Act was established in 1906 and has been used by nearly every President, both Democrats and Republicans, to protect some of our nation's most treasured natural landscapes, historic sites, and cultural heritage.