The Republican governor of Texas, Greg Abbott, is ratcheting up his war of words with the White House over border security, setting the stage for a potential showdown with the federal government over states’ rights the likes of which haven’t been seen in America since the Civil Rights era.

In a letter to President Biden Wednesday, Mr. Abbott suggests that the president is ignoring his constitutional duties to enforce federal laws vis-a-vis immigration and in some cases violating them. He also accuses the president of sending federal lawyers to court to block Texas’ efforts to secure the border and instructing agencies to ignore federal statutes mandating the detention of illegal migrants.

“Under President Biden’s lawless border policies, more than 6 million illegal immigrants have crossed our southern border in just three years,” the letter states. “That is more than the population of 33 different states in this country. This illegal refusal to protect the states has inflicted unprecedented harm on the people all across the United States.”

Mr. Abbott says the framers of the Constitution, in Articles IV and I, sought to require the federal government to protect states from invasion and acknowledge the states’ “sovereign interest” in protecting their borders. He said the framers “foresaw that states should not be left to the mercy of a lawless president who does nothing to stop external threats like cartels smuggling millions of illegal immigrants across the border.”

The letter notes that Mr. Abbott has already declared the crisis at the border an “invasion” and mobilized National Guard troops so the state of Texas can “defend and protect itself” against the invaders.

Mr. Abbott’s letter comes in response to a ruling from the Supreme Court, requested by the Biden administration, stating that federal Border Patrol officers can legally remove razor wire strung up at several locations along the U.S.-Mexico border in order to deter migrants.

Four conservative members of the court — Justices Alito, Thomas, Gorsuch, and Kavanaugh — would have rejected the government’s request, the order noted. Chief Justice Roberts joined with the liberal members of the panel to give the Biden administration its victory.