El Paso, Texas — The Biden administration has finalized a sweeping restriction on asylum that it plans to use to ramp up swift deportations of migrants who cross the U.S.-Mexico border after the Title 42 pandemic-era emergency policy sunsets on Thursday, according to internal documents obtained by CBS News.

Hundreds of U.S. asylum officers were trained on how to enforce the restriction on Tuesday and the regulation is expected to be published on Wednesday, less than 48 hours before Title 42 is set to expire, according to people familiar with the effort who requested anonymity to discuss internal plans.

The regulation, which is expected to be challenged in federal court, will be a dramatic shift in asylum policy, disqualifying migrants from U.S. protection if they fail to request refugee status in another country, such as Mexico, on their journey to the southern border 

The rule also represents a major pivot by President Biden, a Democrat who campaigned on restoring access to the U.S. asylum system after numerous Trump administration rules made it more difficult for migrants to secure refuge on American soil. In fact, the regulation that will be published Wednesday resembles a Trump-era policy struck down in federal court that Mr. Biden decried in 2020.

If upheld, the Biden administration's rule will cement a growing bipartisan rejection of the asylum laws that Congress enacted in 1980 to conform with international treaties designed to prevent nations from turning away refugees to places where they could be persecuted, as the U.S. did to some Jews fleeing Nazi Germany.

The years-in-the-making shift has intensified recently, as historically high levels of migrant arrivals have further strained a massively backlogged asylum system, overwhelmed border communities and created a political liability for Mr. Biden ahead of his re-election bid.