Texas Gov. Greg Abbott has no constitutional authority to define the flow of undocumented immigrants across the Rio Grande as an "invasion" and is usurping powers that belong to the federal government, the U.S. Justice Department says in new court filings.

"Whether and when an 'invasion' occurs is a matter of foreign policy and national defense, which the Constitution specifically commits to the federal government," the Justice Department wrote in a 13-page brief that included nearly 150 pages of supporting material.

"An invasion is 'armed hostility from another political entity, such as another state or foreign country that is intending to overthrow the state’s government,'" the Justice Department added, citing a 1996 decision by the Supreme Court.

The brief, filed late Wednesday in the Western District of Texas, is part of the ongoing litigation brought by the Justice Department against Abbott and the state of Texas over the placement of giant buoys in the Rio Grande near Eagle Pass to deter unlawful immigration. The Justice Department is asking Senior U.S. Judge David Alan Ezra to order the buoys removed pending the outcome of the trial, which has yet to begin.

A hearing on the matter is set for Tuesday in Austin.

Texas border barrier like waging war: legal filing

An earlier filing by lawyers for Abbott and the state defended the placement of the 1,000-foot string of floating barriers, saying governors have broad powers to act without federal authority to defend against an invasion.

And in public remarks and social media posts, Abbott has called the sharp increase in unlawful border crossings, coupled with transnational drug-trafficking, an invasion that threatens Texas' sovereignty.

"The federal government’s FAILURE to secure our border has forced Texas to protect its own territory against invasion by the Mexican drug cartels & mass illegal immigration," said in one tweet from his official government account.

In a "friend of the court" brief filed this week by attorney Matt Crapo of the conservative Immigration Reform Law Institute in support of Texas' position, the rhetoric was even more heated.

Crapo likened Abbott's efforts to curb unlawful immigration, which the governor calls Operation Lone Star, to the waging of war. Crapo said Ezra should reject the Justice Department's request that the buoys be removed because "the Constitution explicitly recognizes that Texas retains its inherent authority to exercise war powers in the event of an invasion, and in doing so is not subject to the control of Congress."

Mexico President Andrés Manuel López Obrador has made clear his objection to the buoys, most of which cross into waters belong to his country.

Buoy immigration:Texas' Rio Grande buoys are mostly on Mexico's side of river, international agency says

In its most recent filing, the Justice Department contends that Texas' buoys not only run afoul of the Rivers and Harbors Act of 1899, which prohibits "the construction of any structure in or over any navigable water" without the approval of the U.S. Army Corps of Engineers, the are also undermining U.S.-Mexico relations.

"The harm to the United States’ conduct of foreign relations is immediate and ongoing, as the evidence shows," the filing says. "Texas’s conduct is already 'the subject of diplomatic concern' between Mexico and the United States," and has concretely disrupted the countries’ cooperative efforts to manage the delivery of water to the United States.

"That the harm might become worse without injunctive relief does not mean no harm is occurring now. Only the prompt removal of the entire Floating Barrier will remedy this harm."

John C. Moritz covers Texas government and politics for the USA Today Network in Austin. Contact him at [email protected] and follow him on Twitter @JohnnieMo.

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