President Donald Trump's immigration agenda is playing out in numerous ways Friday, from hearings in key cases on the government's power to deport people to the start of a registry required for all those who are in the country illegally.

And on Thursday, immigration developments came on multiple fronts as federal officials work on the president's promise to carry out mass deportations and double down on his authority to do so. The Supreme Court ruled in the case of a mistakenly deported man, and the administration's classification of thousands of living immigrants as dead came to light.

Here is a breakdown of some of what has happened so far and what is ahead on the immigration front.

The Supreme Court on Thursday said the Trump administration must work to bring back a Maryland man who was mistakenly deported to a prison in El Salvador.

Kilmar Abrego Garcia is a Salvadoran citizen who had an immigration court order preventing his deportation to his native country over fears he would face persecution from local gangs. But Immigration and Customs Enforcement deported him anyway to El Salvador, where he's been held in a notorious prison.

U.S. District Judge Paula Xinis had ordered Abrego Garcia returned to the U.S. by midnight Monday. The Supreme Court order requires the government to facilitate his release from custody.

The two sides are expected back in a Maryland court Friday, although the Trump administration had asked for a delay until Monday. Abrego Garcia’s lawyers called that request “another stunning display of arrogance and cruelty."

On Friday, Columbia University activist Mahmoud Khalil is expected in immigration court in central Louisiana, where an immigration judge will hear arguments on whether the administration can continue detaining him during his immigration proceedings or whether he should be released as they play out.

Khalil is a 30-year-old Palestinian by ethnicity who was born in Syria. He was arrested March 8 in New York and taken to Louisiana. He is a legal permanent U.S. resident who served as spokesperson for campus activists last year during large demonstrations against Israel’s treatment of Palestinians and the war in Gaza. He finished his coursework for his graduate degree in international affairs last semester.

At the time of Khalil’s arrest, a Department of Homeland Security spokesperson accused Khalil of leading activities “aligned to Hamas,” referring to the militant group that attacked Israel on Oct. 7, 2023.

Since then, the government hasn't produced evidence linking Khalil to Hamas.

In a recent filing, the government instead submitted a memo citing the Trump administration’s authority to expel noncitizens whose presence in the country damages U.S. foreign policy interests.

The two-page memo, signed by Secretary of State Marco Rubio and obtained by The Associated Press, does not allege any criminal conduct by Khalil. Rather, Rubio wrote Khalil could be expelled for his beliefs.

Rubio said Khalil’s activities were “otherwise lawful." But the secretary wrote that letting him remain in the country would undermine “U.S. policy to combat anti-Semitism.”

Khalil has adamantly rejected allegations of antisemitism, accusing the Trump administration of “targeting me as part of a broader strategy to suppress dissent” in a letter sent from jail.

A federal judge said Thursday that she will prevent the Trump administration from ordering hundreds of thousands of Cubans, Haitians, Nicaraguans and Venezuelans with temporary legal status to leave the country later this month.

The ruling is significant for the more than 500,000 people who came to the country under the Biden-era program. They were facing an April 24 deadline by which their work permits would be terminated and they could be subject to deportation.

The program was launched as the Biden administration was generally trying to alleviate pressure on the southern border by creating new pathways for people to come to the U.S. and work, usually for two years on humanitarian parole.

The reprieve may be temporary, as the government is likely to appeal. The Trump administration has harshly criticized Biden's use of humanitarian parole.

During a hearing Thursday, U.S. District Judge Indira Talwani repeatedly questioned the government’s assertion that it could end humanitarian parole for the four nationalities. She argued that immigrants in the program who are here legally now face an option of “fleeing the country” or staying and “risk losing everything.”

Friday marks the launch of a requirement for people who are in the country illegally to register with the federal government.

Homeland Security announced Feb. 25 that it was mandating all people in the U.S. illegally register with the federal government, and said those who didn’t self-report could face fines or prosecution. Failure to register is considered a crime, and people will be required to carry registration documents with them or risk prison time and fines.

The registration process also applies to Canadians who are in the U.S. for more than 30 days, including so-called snowbirds who spend winter months in places such as Florida.

Opponents sued to stop the registry from taking effect, saying the government should have gone through the more lengthy public notification process, and that it’s enforcing this simply to facilitate Trump’s aim of mass deportations.

On Thursday, a federal judge sided with the administration. Officials had argued they were simply enforcing a requirement that already existed for everyone who is in the country but isn’t an American citizen.

Immediately after the ruling, Department of Homeland Security officials emphasized that going forward, the registration requirement would be enforced to the fullest.

Questions remain about how the registration requirement will function. But its impact could be far-reaching. The Trump administration has said between 2.2 million and 3.2 million people could be affected.

In an effort to make more migrants voluntarily go home, the Trump administration is classifying more than 6,000 immigrants — who are alive — as dead. They're canceling their Social Security numbers and effectively wiping out their ability to work or receive benefits in the U.S. That is according to two people familiar with the situation who spoke on condition of anonymity because the plans had not yet been publicly detailed.

The move will make it much harder for those affected to use banks or other basic services where Social Security numbers are required. It’s part of a broader effort by Trump to crack down on immigrants who were allowed to enter and remain temporarily in the United States under programs instituted by his predecessor, Joe Biden.

The officials said stripping the immigrants of their Social Security numbers will cut them off from many financial services and encourage them to “self-deport” and abandon the U.S. for their birth countries.

It wasn’t immediately clear how the immigrants were chosen. But the Trump White House has targeted people in the country temporarily under Biden-era programs.

Earlier this week, the Department of Homeland Security and Treasury signed a deal allowing the IRS to share immigrants’ tax data with Immigration and Customs Enforcement for the purpose of identifying and deporting people illegally in the U.S.

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Associated Press reporters Rebecca Santana, Jake Offenhartz, Will Weissert, Fatima Hussein, Mark Sherman and Michael Casey contributed.