A federal judge on Thursday blocked Texas authorities from enforcing key parts of a law that would allow state officials to arrest and deport people ​suspected of having illegally crossed the U.S.-Mexico border.

Austin-based U.S. District Judge David Ezra issued a preliminary injunction at the behest of the American Civil Liberties Union and other groups pursuing a class action on behalf of thousands of people who could be subject to the law's provisions.

Ezra, who was appointed by Republican President Ronald Reagan, said the state law ​was preempted by federal law and improperly challenged the federal government's ⁠long-held power to control immigration, naturalisation, and deportations.

"At the broadest level, SB 4 conflicts ​with federal immigration law because it provides state officials the power to enforce federal law ​without federal supervision," Ezra wrote.

Spokespeople for Republican Attorney General Ken Paxton, whose office is defending the law, did not respond to requests for comment.

The lawsuit was filed last week to prevent parts of the ​2023 law from taking effect, after a federal appeals court in April overturned an earlier ​injunction issued during Democratic President Joe Biden's administration that had prevented the Republican-backed measure known as SB ‌4 ⁠from being enforced.

Republican President Donald Trump's administration had dropped a case the Biden administration brought challenging the law. Immigrant-rights groups that had also sued pressed on, but the 5th U.S. Circuit Court of Appeals concluded the organizations lacked legal standing to pursue their case.

The ​new ACLU-backed lawsuit sought ​to address that ⁠issue by instead suing on behalf of noncitizens who could be subject to four key provisions of the law, which is set ​to take effect on Friday.

Those provisions include ones that make ​it a ⁠state crime for someone to reenter the U.S. after deportation, even if they have federal permission to do so or have since obtained a green card, and that give magistrate judges ⁠in ​Texas the power to issue deportation orders.

Lawyers for the ​plaintiffs in a joint statement hailed Ezra's ruling.

"Texas cannot override the U.S. Constitution and should stop wasting time ​attempting to do so," they said.