A Texas federal judge issued a preliminary injunction on Thursday suspending enforcement of a Texas state law that criminalized illegal entry to the US from abroad. The law, SB4, criminalized a number of immigration offenses under state law and empowered state law enforcement to make arrests and hold people in detention. SB4 will now be on hold while challenges against it proceed.

Judge David Alan Ezra, the Senior District Judge for the Western District of Texas Austin Division, wrote that “several factors” justified granting a preliminary injunction and suspending the law. The first and foremost reason is that the Supremacy Clause of the US Constitution and Supreme Court precedent grant immigration enforcement powers to the federal government. States only have immigration enforcement power when it is granted to them by the federal government. Specifically, he cited Arizona v. United States, which struck down a similar law in Arizona and affirmed that “the Government of the United States has broad, undoubted power over the subject of immigration.” This means that SB4’s attempt to regulate immigration is preempted by federal law. In addition, Judge Ezra said that SB4, “conflicts with key provisions of federal immigration law, to the detriment of the United States’ foreign relations and treaty obligations.”

Texas has defended its attempts to regulate immigration at the state level by saying the state is defending itself from an invasion. Ezra rejected this, saying that surges in immigration “do not constitute an ‘invasion'” and that Texas is not fighting a war by enforcing SB4. He went on to say that allowing Texas to use this justification to supersede federal law would amount to nullification, which is “a notion that is antithetical to the Constitution and has been unequivocally rejected by federal courts since the Civil War.” Because of these reasons, Ezra said the plaintiffs met the standard for a preliminary injunction, including proving a likelihood of succeeding on the merits.

The ACLU of Texas, who filed the lawsuit challenging SB4 on behalf of a group of plaintiffs, celebrated the decision, saying it affirms federal supremacy in immigration law and protects immigrant communities. David Donatti (he/him), senior staff attorney at the ACLU of Texas, said:

The court’s decision to block this anti-immigrant law from taking effect is an important win for Texas values, human rights, and the U.S. Constitution. Our current immigration system needs repair because it forces millions of Americans into the shadows and shuts the door on people in need of safety. S.B. 4 would only make things worse. Cruelty to migrants is not a policy solution.

Texas Governor Greg Abbott, who has led the charge to pass immigration laws in Texas, condemned the decision in a press release. He said the state would appeal and suggested it would reach the US Supreme Court:

Texas has the right to defend itself because of President Biden’s ongoing failure to fulfill his duty to protect our state from the invasion at our southern border. Even from the bench, this District Judge acknowledged that this case will ultimately be decided by the U.S. Supreme Court.

The ruling is just the latest update in an escalating dispute between Texas and the federal government over immigration. Abbott continues to claim that Texas has a “right of self-defense” and has taken a number of actions to shut down the southern border, including passing SB4 and setting up floating barriers in the Rio Grande River. Tensions between the state and federal governments recently came to a head when two migrant children and their mother died because Texas law enforcement refused to grant federal officials access to the border to administer emergency aid.