For more than a century, immigration and border enforcement have been seen as falling exclusively under federal control, and when states tried to exert a greater role, courts shut them down.

Texas is now moving to challenge that legal interpretation before the U.S. Supreme Court’s current conservative majority. And the outcome may turn on a lone 2012 dissent by the late conservative Justice Antonin Scalia.

Scalia insisted it was a myth that the Constitution gave the federal government exclusive power over immigration. He noted that most federal immigration laws did not come into existence until the 1880s, and that before that, states put their own limits on who could enter.

He referred to the U.S. as “an indivisible union of sovereign states” and said lax federal enforcement of immigration laws deprives “sovereign” states like Texas and Arizona of “the power to exclude … people who have no right to be there. … The states have the right to protect their borders against foreign nationals.”

Moreover, he argued that even when federal law supersedes state law, that shouldn’t prevent states from participating in enforcement of the federal law.

No other justice signed on to Scalia’s opinion; his view of “sovereign” states was seen by many as extreme and outdated.

But that dissent is now fueling the immigration and border control dispute between Texas and the Biden administration.

And if today’s more conservative Supreme Court adopts Scalia’s view, it could redefine the balance of power between federal government and the states, and clear the way for aggressive state enforcement of immigration laws.

Last week offered a preview. In a 5-4 vote, the justices sided with President Biden’s Homeland Security Department and set aside an appeals court order that prohibited U.S. Border Patrol agents from cutting through razor wire that had been installed by the state of Texas along the Rio Grande and that was blocking federal agents from patrolling the area.

But the one-line order was limited, and said nothing about Texas’ authority to block migrants from entering the state, including with razor wire along the river.

Texas Gov. Greg Abbott, citing Scalia’s 2012 dissent, vowed to press the legal fight.

“The federal government has broken the compact between the United States and the States,” the Republican governor said in a statement released after last week’s Supreme Court order. “The Executive Branch of the United States has a constitutional duty to enforce federal laws protecting states, including immigration laws on the books right now. President Biden has refused to enforce those laws and has even violated them.”

A day later, 25 Republican governors released a statement saying that they “stand in solidarity” with Abbott and Texas in using “every tool and strategy, including razor wire fences, to secure the border.”

Next week, the 5th U.S. Circuit Court of Appeals in New Orleans will hear arguments in the dispute over razor wire. If Texas wins there, the case will likely return to the Supreme Court.

But a far more significant case is headed there soon.

In December, Abbott signed into law SB 4, a measure authorizing police and judges in Texas to arrest,detain and deport migrants who are suspected of crossing the border illegally.

The measure is seen as a direct challenge to the 2012 Supreme Court decision that struck down a similar law in the case of Arizona vs. United States. It was that decision that prompted Scalia’s dissent.

“This is a frontal assault on the federal primacy in immigration enforcement, and it’s definitely going to the Supreme Court,” said Cornell law professor Stephen Yale-Loehr.

Thomas Saenz, president of the Mexican American Legal Defense and Educational Fund, called the Texas measure “the most extreme encroachment on exclusive federal authority that we have seen in at least 50 years,” saying that “it goes beyond California’s Prop. 187 and Arizona’s SB 1070 by seeking to set up the state’s own system of immigration courts and enforced deportation orders.”

He warned: “If that were the law, we could have 50 different immigration systems in this country.”

But he predicted that not even a Supreme Court as conservative as today’s would uphold the Texas law.

“This is essentially political theater for Abbott. It will get attention for him and inspire the base,” he said.

In early January, the Biden administration filed a lawsuit in Austin, the state’s capital, seeking to block the Texas law from taking effect on March 5 as planned.

“SB 4 is clearly unconstitutional,” outgoing Associate U.S. Atty. Gen. Vanita Gupta said at the time. “Under the Supremacy Clause of the Constitution and longstanding Supreme Court precedent, states cannot adopt immigration laws that interfere with the framework enacted by Congress.”

The lawsuit says that it seeks to preserve the U.S. government’s “exclusive authority … to regulate the entry and removal of non-citizens,” and that the nation “must speak with one voice in immigration matters.”

Immigration rights advocates have also voiced alarm about the Texas measure, saying it could be used against vast numbers of noncitizens who live far from the border.

“This law will rupture Texas communities,” said Adriana Piñon, legal director at the American Civil Liberties Union of Texas, which has also sued to block the law. “It will strip people of their rights under federal law with devastating consequences: Families may be separated, more people may live in fear of law enforcement, and migrants may have a harder time fully integrating into our communities.”

The Constitution establishes U.S. laws as “the supreme law of the land,” which states are bound to follow.

Scalia did not contest that principle, and agreed states that may not adopt or enforce laws that directly conflict with immigration laws adopted by Congress.

“I accept as a given that state regulation is excluded by the Constitution when (1) it has been prohibited by a valid federal law, or (2) it conflicts with federal regulation — when, for example, it admits those whom federal regulation would exclude, or excludes those whom federal regulation would admit,” he wrote.

But he disagreed with the court’s majority, which held that states like Arizona may not use their police to enforce immigration laws in ways that go beyond federal policy.

Writing for the court, then-Justice Anthony M. Kennedy said that the “national government has significant power to regulate immigration,” and that the “states may not pursue policies that undermine federal law.”

The justices blocked three parts of the Arizona law, including provisions that made it a state offense for an “unauthorized alien” to apply for work or to fail to carry registration documents.

But the court stopped short of blocking a fourth provision, seen as highly controversial at the time, that said police may seek to “determine the immigration status” of any person they stop, detain or arrest if there is reason to believe the person is “unlawfully present in the United States.”

To many, the ruling on Arizona’s law stood as a warning that conservative states may not pursue immigration enforcement that goes beyond the policies and priorities set by the administration in Washington.

That understanding is now being put to the test.

Chief Justice John G. Roberts Jr., whose votes are largely conservative, joined Kennedy in the Arizona case, and sided last week with the Biden administration in the Texas dispute over razor wire.

Justice Amy Coney Barrett, a conservative, cast a key vote for the majority in the Texas case, along with liberal Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson.

Justices Clarence Thomas and Samuel A. Alito Jr., both conservatives, dissented in the 2012 Arizona case — though they did not join Scalia’s statement of dissent — and did the same last week in the Texas case, along with fellow conservative Justices Neil M. Gorsuch and Brett M. Kavanaugh.

If a federal judge in Austin or the 5th Circuit refuses to block SB 4, the justices are likely to face another emergency appeal from the Biden administration by the end of this month.