A federal appeals court has frozen Texas’s controversial immigration law, one of the toughest laws of its kind enacted by a US state in modern times.
The decision came just hours after the Supreme Court allowed the measure, SB4, to take effect pending an appeal.
The legislation would allow officials in Texas to detain and prosecute unauthorised migrants.
Mexico, which borders Texas, has said it will refuse to accept any migrants deported by its authorities.
Migrant arrivals at the southern US border have risen to record highs during President Joe Biden’s administration, making it a top concern among US voters ahead of November’s presidential election.
The SB4 law in Texas was due to come into effect on 5 March but the Biden government has challenged it, calling it unconstitutional.
The decision to freeze the law is the latest in a string of judicial rulings deciding its fate.
If it were to come back into effect, it would mark a significant shift in how immigration enforcement is handled, as courts have previously ruled that only the federal government can enforce the country’s immigration laws – not individual US states.
Crossing the US border illegally is already a federal crime, but violations are usually handled as civil cases by the immigration court system.
Under SB4, punishments for illegal entry or re-entry into Texas range up to 20 years in prison.
It is not clear if any migrants were detained during the few hours the law was briefly in effect.
The Mexican foreign ministry said in a statement on Tuesday: “Mexico categorically rejects any measure that allows state or local authorities to exercise immigration control, and to arrest and return nationals or foreigners to Mexican territory.”
Legal back-and-forth
The ruling is the latest in a back-and-forth of court rulings over whether SB4 can go ahead.
In January, the Biden administration sued the state of Texas, arguing that issues of immigration were a federal matter.
In February, a district court ruled that SB4 was illegal, and blocked it from taking effect over concerns it would lead to each US state having its own immigration laws.
Soon after, the New Orleans-based US Court of Appeals for the Fifth Circuit – the federal appeals court responsible for the area – said the law may take effect as it considered the appeal, unless the Supreme Court intervened.
The Biden administration then filed an emergency request to the Supreme Court to uphold the district court’s freeze while the litigation was under way.
In the meantime, Supreme Court Justice Samuel Alito placed a hold on the law to give the courts time to decide how it should proceed.
Earlier on Tuesday, the Supreme Court allowed the measure to take effect while a lower federal appeals court weighed its legality.
Then in a brief order late on Tuesday night, a three-judge panel at the Fifth Circuit voted to freeze the ruling as it hears the appeal.
A court session has been scheduled for Wednesday.
Historically, the federal government has created laws and regulations on immigration, even though the US Constitution does not explicitly grant it those powers.
It is also the federal government that negotiates treaties and agreements with other countries.
Republicans often criticise Democratic President Biden’s handling of the US-Mexico border, which opinion polls suggest is a prime concern for voters ahead of November’s White House election.
A Gallup poll released in February suggested that nearly one-third of Americans believe immigration was the single greatest problem the country faced ahead of the government, the economy and inflation.
