President-elect Donald Trump has vowed a crackdown on immigration like never before.

While his hard-line rhetoric about illegal immigration harks back to his first campaign, one of Trump’s targets this time is a decades-old program providing temporary legal status to about 1 million immigrants from dangerous and deeply troubled countries such as Haiti and Venezuela.

Known as Temporary Protected Status, the program was signed into law by President George H.W. Bush to help people already in the United States who cannot return safely and immediately to their country because of a natural disaster or an armed conflict.

But for some immigrants, the program, which allows them to work legally, has become all but permanent, a reflection of how troubled many corners of the world are and how little Congress has done to adapt the U.S. immigration system to the realities of global migration in the 21st century.

About 200,000 people with TPS are from Haiti, a long-troubled island nation where the assassination of the president in 2021 led to the collapse of the government and the killings of thousands of people by gangs that now control much of the country. Haitians have emerged as the focus of Trump’s threats to effectively end the program after he and his running mate, Sen. JD Vance, spread false rumors that Haitians who have settled in Springfield, Ohio, were abducting and eating pets.

Thousands of Haitians have settled in the city, and the majority of them have lawful status, often through the program. That has made them attractive to local industries in need of workers. But the influx has strained resources and caused friction among some residents, and Trump seized on those tensions, vilifying the Haitians who have made Springfield home and threatening to effectively end the program for them and hundreds of thousands of other immigrants.

“Absolutely I’d revoke it,” Trump said in an interview with News Nation last month, adding that he would send the immigrants back to their country.

Vance, for his part, has repeatedly characterized Haitians in Springfield and other TPS holders as “illegal aliens” granted “amnesty” by the Biden administration at the wave of a “magic government wand.”

“We’re going to stop doing mass grants of Temporary Protected Status,” Vance said at a campaign event last month.

The biggest group of people granted protection under the program — about 350,000 — comes from Venezuela, where political repression and economic collapse under the Maduro regime have led millions to leave in recent years.

Immigrants from some countries, including El Salvador, Honduras and Nicaragua, have been eligible for the protection for more than two decades. Other countries, including Ethiopia, Lebanon and Ukraine, were added more recently.

Proponents of limiting immigration have been critical of the program, which they say allows people who receive the designation to ultimately stay in the United States indefinitely.

Trump’s advisers have made clear that his administration will reverse course on TPS, and his early choices for key immigration roles include notable hard-liners.

The secretary of homeland security decides whether conditions in a given country merit granting its nationals protected status. The status lasts six to 18 months at a time and can be renewed indefinitely, so long as conditions warrant. Immigrants in the United States, whether they entered legally or not, are eligible for the status, which does not place them on a path to permanent legal residency, or green cards.

The Biden administration has renewed, reinstated or added protections for 16 countries.

Ending the program could uproot people who have been in the United States for years. Many would have to quit their jobs and return to troubled countries, and some families with U.S.-born children could end up separated, with parents forced to leave the country while their sons and daughters remain.

The Obama administration offered the special status to Haitians in the United States in 2010, after a cataclysmic earthquake devastated the capital and killed at least 250,000 people. At the time, the homeland security secretary, Janet Napolitano, noted that the program would allow Haitians to work legally and send money home to family members, which she called an indirect form of aid.

Since the assassination of the country’s last president in 2021, Haiti has plunged into political chaos and been plagued by gang violence that killed thousands of people and made water, food and health care far harder to obtain.

Lesly Joseph, a Haitian dentist, and his wife, flew to the United States in 2021 on tourist visas after being threatened at gunpoint by gangs. The couple felt fortunate, he said, when the Biden administration designated Temporary Protected Status for nationals of Haiti, based on the spiraling violence within a day of their arrival.

“TPS offered me sanctuary to live here and protect my family from harm,” said Joseph, who lives in Boston and has a 3-year-old American daughter.

Returning to Haiti would be akin to a death sentence, Joseph said, noting that a physician friend had been killed by gangs this week.

The Trump administration tried to scrap the program in 2017 and 2018 for El Salvador, Haiti, Honduras, Nepal, Nicaragua and Sudan, and was sued in federal court. The administration argued that the program had turned into a quasi-permanent benefit for hundreds of thousands of people.

The American Civil Liberties Union won a preliminary injunction to keep the program in place, and the Trump administration appealed the decision. The case was still before the 9th U.S. Circuit Court of Appeals when Trump left office in 2021, but it became moot after the Biden administration signaled its support for the program.

Now, with three of Trump’s nominees part of a conservative supermajority on the Supreme Court and many more elsewhere in the federal judiciary, a renewed effort to end TPS could fare better in the courts.