According to news reports, Mexico is challenging Texas’ floating barrier plan on Rio Grande. This is the story:
Mexico’s top diplomat said Friday her country has sent a diplomatic note to the U.S. government expressing concern that Texas’ deployment of floating barriers on the Rio Grande may violate 1944 and 1970 treaties on boundaries and water.
Foreign Relations Secretary Alicia Bárcena said Mexico will send an inspection team to the Rio Grande to see whether any of the barrier extends into Mexico’s side of the border river.
She also complained about U.S. efforts to put up barbed wire on a low-lying island in the river near Eagle Pass, Texas.
I don’t know if Mexico has a case. I’m not familiar with border treaties. At the same time, Texas claims that the barrier is on the Texas side of the water.