Texas authorizes access to nine islands
The Texas General Land Office, headed by Commissioner Dawn Buckingham, announced the claim on October 26, 2026. It identified roughly 66 acres across nine islands as Texas property and said the determination settled jurisdictional uncertainty, allowing the Texas Department of Public Safety and the Texas Military Department to access, monitor and protect them.
Buckingham also gave the agencies permission to enter the islands for southern border security operations. Her October 26 letters went to Major General Thomas Suelzer, commander of the Texas Military Department, and Colonel Freeman Martin, director of the Texas Department of Public Safety.
The islands are along the river between Laredo and McAllen. A map accompanying the letters lists Nixon Island at 21.7 acres, McKendricks Island at 18.4 acres, Zachary Island at 12.5 acres and Clark Island at 3.6 acres. Miller Island, the smallest, covers 0.5 acres.
Mexico points to treaty rules
Mexico issued its response in informative note No. 015/2026 on October 30, four days after the Texas announcement. The note named neither Texas officials nor individual islands and announced no complaint, summons or request to the International Boundary and Water Commission.
The ministry said the 1970 Mexico-U.S. Boundary Treaty places the river boundary at the center of the channel carrying its normal flow. That line establishes sovereignty over land on either side, irrespective of which country previously held sovereignty there. The Rio Grande is known in Mexico as the Rio Bravo.
The two national governments have entrusted the International Boundary and Water Commission with implementing the treaty, the ministry said. Deciding which side of the border an island occupies is the commission's responsibility, not a state government's.
Signed in Mexico City on November 23, 1970, the treaty took effect on April 18, 1972. Article II establishes the river boundary and requires the commission to resurvey it at least once every 10 years.
The ministry also said Article IV requires both sections of the commission to consider and approve any proposed work or action on the disputed islands. Neither country may construct works that the commission determines could change or obstruct the river's normal flow.
Gabriel Eckstein, a Texas A&M University water law scholar and president of the International Water Law Association, told EL PAÍS English that the central issue was whether the islands belonged to the U.S. federal government or Texas, rather than whether Texas was taking Mexican islands. He rejected Texas' premise that the islands had no owner, saying international treaties had already established the boundary and title.
Mexico said it would watch developments in the area closely, honor the boundary treaty and maintain dialogue through the established mechanisms.
Earlier Texas island declarations
The land office linked its latest claims to Buckingham's 2023 declaration that Fronton Island, a 170-acre island in Starr County, was state land. After that declaration, the Texas Department of Public Safety and the Texas Military Department removed vegetation under Operation Flat Top. The land office says the operation helped disrupt criminal activity on the island.
On March 31, 2025, the office announced another state-land declaration covering two islands near Roma in Starr County, measuring about 12.13 and 20.3 acres. Describing one as cartel-infested, it asked the Trump administration and the Texas Military Department to secure it.
