The Department of Justice is ready to sue Gov. Greg Abbott over the floating buoy barrier he deployed in the Rio Grande to block migrants from crossing the river from Mexico into Texas near Eagle Pass.

The DOJ sent Abbott a letter on Thursday warning that the state’s buoy barrier is unlawful.

“The State of Texas’s actions violate federal law, raise humanitarian concerns, present serious risks to public safety and the environment, and may interfere with the federal government’s ability to carry out its official duties,” the department wrote, according to a copy obtained by Hearst Newspapers.

Assistant Attorney General Todd Kimm and Jaime Esparza, United States Attorney for the Western District of Texas, go on to write that the wall of buoys violates the Rivers and Harbors Act, which prohibits the creation of any obstruction to the navigable capacity of waters of the United States. They further point out that Texas did not seek authorization from the U.S. Army Corps of Engineers to deploy the barrier, which is required by the law.

“This floating barrier poses a risk to navigation, as well as public safety, in the Rio Grande River, and it presents humanitarian concerns. Thus, we intend to seek appropriate legal remedies, which may include seeking injunctive relief requiring the removal of obstructions or other structures in the Rio Grande River,” the letter states.