(The Center Square) – While Gov. Greg Abbott has yet to issue a formal invasion declaration, on Wednesday he took what many believe was the most significant step toward doing so.

Abbott sent a letter to President Joe Biden saying Texas was “escalating” its border security efforts and was invoking “Article I, § 10, Clause 3 of the U.S. Constitution, thereby enabling the State of Texas to protect its own territory against invasion by the Mexican drug cartels.”

The Texas governor also said that by the president “opening our border to this record-breaking level of illegal immigration, you and your Administration are in violation of Article IV, § 4 of the U.S. Constitution. Your sustained dereliction of duty compels Texas to invoke the powers reserved in Article I, § 10, Clause 3, which represents ‘an acknowledgement of the States’ sovereign interest in protecting their borders,’” citing Justice Antonin Scalia in Arizona v. US.

Abbott also said the nation’s founders knew a future president might abandon his constitutional duty. He writes, “Know this: Article I, § 10, Clause 3 is not just excess verbiage. It reflects an understanding by our Founders, the authors of the Constitution, that some future President might abandon his obligation to safeguard the States from an extraordinary inflow of people who have no legal right of entry.

“They foresaw your failures. In the more than 240 years of our great nation, no Administration has done more than yours to place the States in ‘imminent Danger’ – a direct result of your policy decisions and refusal to deliver on the Article IV, § 4 guarantee. In the absence of action by your Administration to secure the border, every act by Texas officials is taken pursuant to the authority that the Founders recognized in Article I, § 10, Clause 3.”

Abbott also vowed that Texas would “escalate our efforts to repel and turn back any immigrant who seeks to enter our State at a border crossing that Congress has designated as illegal; to return to the border those who do cross illegally; and to arrest criminals who violate Texas law.”

His letter reiterates claims from his July 7 executive order first citing his constitutional authority to secure the Texas border. In it, he directed the Texas National Guard and Texas Department of Public Safety to arrest illegal foreign nationals for state crimes and apprehend those who enter Texas illegally in-between ports of entry and return them to ports of entry.

Until he changes the order’s directive, officers working through the state’s border security mission, Operation Lone Star, will continue to apprehend illegal foreign nationals in a supportive capacity to U.S. Border Patrol agents.

Since July 5, Abbott has been urged by county judges to use his full constitutional authority to formally declare an invasion and repel it, including preventing entry into Texas and removing those illegally in Texas back to Mexico. In a letter to judges on Monday, Abbott referred to his July 7 order and the unprecedented measures Texas has taken to secure its border and to a letter he sent TMD and DPS heads “to defend Texas against what amounts to an invasion of America’s southern border.”

If Texas does formally declare an invasion, it would be the first to do so in over 100 years. Tennessee and Georgia invoked the same constitutional clause, known as the Compact Clause, when it asked the federal government for aid during the War of 1812 and received it during the Creek War of 1813 and 1814. An injured soldier and survivor of the war, Sam Houston, would nearly 50 years later, as Texas’ most famous governor, call on the federal government for aid to “repel invasion.”

In February and March of 1860, Houston wrote to U.S. Secretary of War John B. Floyd, saying he felt it was not only his “duty to repel invasion” but also “to adopt such measures as will prevent the recurrence of similar inroad upon our frontiers.”

“Texas is ready for an emergency and will act at a moment’s warning,” Houston wrote. “Texas needs, to repel invasion both from the Indians and Mexico, an immediate supply of arms.”

Over 160 years later, another Texas governor asked the federal government for aid, and none came. Over the past nearly two years, Abbott has written the president urging him to enforce federal immigration law. He also launched OLS, fully funded by Texas taxpayers.

On Wednesday, Abbott became the first governor in U.S. history to notify a president that he’d abandoned his constitutional duty first required by the states when they ratified the constitution in 1788.

Abbott told Biden, “The U.S. Constitution won ratification by promising the States, in Article IV, § 4, that the federal government ‘shall protect each of them against Invasion.’ By refusing to enforce the immigration laws enacted by Congress, including 8 U.S.C. § 1325(a)(1)’s criminal prohibition against aliens entering the United States between authorized ports of entry, your Administration has made clear that it will not honor that guarantee.”

He said Biden must “fulfill your constitutional duty to enforce federal immigration laws and protect the States against invasion. Your silence in the face of our repeated pleas is deafening. Your refusal to even visit the border for a firsthand look at the chaos you have caused is damning.

“Two years of inaction on your part now leave Texas with no choice but to escalate our efforts to secure our State. Your open-border policies, which have catalyzed an unprecedented crisis of illegal immigration, are the sole cause of Texas having to invoke our constitutional authority to defend ourselves.”

Biden hasn’t yet replied. Those in his administration, including Vice President Kamala Harris and DHS Secretary Alejandro Mayorkas, have consistently maintained “the border is secure.”