Tyler, Texas - A federal judge on Thursday struck down President Joe Biden's program aimed at helping undocumented spouses of US citizens obtain legal status, dealing a blow to some half a million people who would have been eligible.

The ruling comes just days after Donald Trump swept to victory in the presidential election on promises of launching a mass deportation of immigrants.

The Keeping Families Together policy, which had been previously suspended amid a court challenge, allowed certain undocumented immigrants married to US nationals to apply for permanent residency without leaving the country, as was previously required.

Judge J. Campbell Barker, of the Eastern District of Texas, who was nominated by Trump during his first White House term, ruled that federal agencies "lack statutory authority" for the program.

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Biden announced Keeping Families Together in June at the height of his reelection bid, before dropping out of the race the next month.

A coalition of Republican-led states including Texas filed suit to block the program, arguing it would cost them millions of dollars in public services, including healthcare, education, and law enforcement.

Keeping Families Together would have applied to immigrants who have been in the country for at least 10 years and were married to a US citizen before June 17, 2024, and also apply to an estimated 50,000 stepchildren of US citizens.

Judge Barker temporarily halted the program in August, and then again after an appeals court lifted the stay.

Biden officials could appeal Barker's ruling, but the incoming Trump administration is unlikely to defend the initiative.

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"Today's decision is a deeply disappointing and unjust setback for the families who live every day under the weight of uncertainty," said Harold A. Solis, co-legal director of Make The Road New York, an NGO supporting immigrants.

"'Keeping Families Together' and everything it represents – family unity, opportunity and stability – is our immigration system at its best. We must and will continue to support family unity despite today's dangerous decision."