Austin, TX (KRGV) — Mexico is disputing Texas' claim to nine islands in the Rio Grande and says only the International Boundary and Water Commission can decide which side of the border they fall on, according to Mexico's Ministry of Foreign Affairs.

The statement issued on Friday was in response to the Texas General Land Office announcing that nine islands along the Rio Grande are now Texas land, giving law enforcement clear access to patrol and inspect them.

"Now that the GLO has confirmed these nine islands belong to the State of Texas, we are notifying our law enforcement partners so that they can gain access to these state-owned properties to patrol, inspect, and clear them of any illegal activity they may encounter, consistent with the law," Texas Land Commissioner Dawn Buckingham said.

Mexico’s Ministry of Foreign Affairs said in a statement the border between Mexico and the United States cannot be changed by a state government decision because its limits are defined by criteria established in an international treaty.

READ MORE: Following Fronton Island model, Texas moves to control and patrol 9 Rio Grande islands

“The 1970 Boundary Treaty between Mexico and the United States establishes that, in the Rio Grande, the international boundary runs along the center of the river's normal channel. This boundary determines the sovereignty of the lands on both sides of the border, regardless of any prior sovereignty those lands may have held,” the ministry said. “The International Boundary and Water Commission is the body authorized by both governments to implement the Treaty and determine which side of the boundary each island falls on. No state authority has this power.”

The statement said Mexico will continue monitoring actions in the area as it commits to complying with the treaty. 

State officials say the decision gives law enforcement clear access to check the islands and keep them from becoming hideouts for smuggling or trafficking. Buckingham also said the state has not confirmed criminal activity on the additional islands.

Texas plans to use Fronton Island near Roma as a model for managing the newly recognized islands. Fronton Island has been under full state control since 2023 after the federal government disputed Texas' claim to it.

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