In brief
The Mexican government has stated that the U.S.-Mexico border cannot be altered by a state government and that sovereignty over the Rio Grande islands falls under the 1970 Boundary Treaty. Mexico reaffirmed the role of the International Boundary and Water Commission and warned against unilateral actions that might divert river flow. The statement comes amid Texas' recent declaration of the islands as part of the state of Texas, raising questions about the diplomatic and legal processes governing the border.
Mexico’s Foreign Ministry issued a firm statement on Friday, October 30, rejecting the Texas General Land Office’s claim that nine islands in the Rio Grande belong to the state of Texas, and underscored that changes to the U.S.-Mexico border cannot be decided by any U.S. state authority. The ministry’s comment was published through Xinhua, noting that the dispute centers on the delineation of sovereignty along the Rio Bravo River, which forms part of the international boundary.
In the ministry’s release, officials reiterated the principles established by the 1970 Mexico‑United States Boundary Treaty, which remains the primary legal framework governing the two countries’ shared frontier. Under the treaty, the international boundary within a river is defined by the “center line of the normal channel,” and that line determines which country owns the land situated to either side. The treaty specifically states that past sovereignty of the islands does not alter the current alignment of the boundary line, making the claim of state sovereignty invalid under international law.
The statement also highlighted the role of the International Boundary and Water Commission – a joint U.S.–Mexico body authorized by both governments to administer all aspects of the treaty. According to the ministry, the commission has the sole authority to determine which side of the center line of the river each island lies, and no state‑level government can override that decision. The commission’s mandate includes resolving disputes about land and water rights that may arise as a result of shifting river courses, which often occur over decades.
Commissioner Dawn Buckingham, who heads Texas’ General Land Office, had issued a declaration earlier that month claiming that the islands were under Texas jurisdiction. The Texas agency argued that the islands had historically been viewed as part of the state, citing regional maps and historical references. However, the commission’s mandate supersedes any claims from local authorities, and the ministry’s comment reiterated that unilateral actions by a state government would be unlawful and could potentially alter the river’s normal flow, a step that the treaty expressly forbids.
Mexico’s Foreign Ministry warned that any construction or water‑management activities on the islands that might shift the river’s course would be considered a violation of the treaty. The ministry emphasized that the treaty obligates both countries to prevent any obstructions or alterations to the normal flow, reinforcing the importance of maintaining the river’s natural behavior. The ministry also noted that it would closely monitor any actions in the area, reminding authorities that a permanent change to the border would require a formal bilateral agreement, not a unilateral federal or state decision.
The 1970 treaty, signed at a time when binational disputes were preeminent, forms part of a broader set of agreements that Mexico and the United States have used to manage shared resources. The treaty’s language has been repeatedly cited in boundary disputes, including earlier cases involving the disputed islands, and has consistently been upheld in diplomatic negotiations. The article from Xinhua underscores that the boundaries, whether on land or water, are defined by international treaty rather than regional or state politics.
In response, the Mexican ministry invited dialogue through established mechanisms, underscoring the principle of continued cooperation. By stating it would “pursue dialogue through established mechanisms,” officials reaffirmed their willingness to engage in discussions with the United States through the traditional channels that govern border issues, including the commission.
The Texas General Land Office has yet to issue a follow‑up statement following the ministry’s denouncement. The lack of a public rebuttal from the Texas agency leaves an open question regarding how the state might proceed if the claim rests on a misinterpretation of historical documents or current treaties.
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