Nearly two million people have been expelled at the northern and southwest land borders under the controversial order, known as Title 42, on the basis that allowing them into the U.S. immigration system during the pandemic poses a threat to Americans’ health.

“Right now Title 42 is the only policy they have to manage the volume of arrivals at the border,” said Theresa Cardinal Brown, managing director of immigration and cross-border policy at the Bipartisan Policy Center. “If [it] were to come down suddenly, they would be required to take into custody everybody they encounter and process their asylum claims. They would have a big logistical problem on their hands.”

The administration has said it is preparing for that possibility. The Centers for Disease Control and Prevention — the agency responsible for invoking the policy in 2020 — says it is now evaluating the order, which comes up for review every 60 days and ends on March 30.

“We last reassessed Title 42 at the end of January. As you recall, that was just around or right after the peak of our Omicron surge and we had hospital capacity challenges really across the country,” CDC Director Rochelle Walensky said at a Wednesday press briefing. “ We are currently reviewing the data and evaluating it.”

A confluence of events this month brought the policy renewed scrutiny. On March 4, a D.C. Circuit Court judge questioned what, if any, public health purpose the policy serves at this stage in the pandemic. A week later, the CDC, in response to a separate court ruling in Texas, ended the order for unaccompanied minors, but kept it in place for adults and families.

Since then, Ukrainians fleeing the Russian invasion have also run up against Title 42 — and in some cases been exempted. A March 11 memo obtained by POLITICO from U.S. Customs and Border Protection reminds staff that the CBP is permitted under Title 42 to make exceptions, including for Ukrainian nationals, on a case-by-case basis. The CBP did not respond to a request for information on how many have been made.

To critics of the policy, all of these developments undermine its justification of protecting Americans’ health, and further chip away at the reputation of the CDC at a moment when it is trying to regain the nation’s trust.

“From a public health point of view — in terms of providing protection to people residing in the United States — this does nothing,” says Ron Waldman, a former CDC epidemiologist and professor emeritus at George Washington University’s Milken Institute School of Public Health. “The CDC as a public health agency needs to be guided first and foremost by the science. I believe in this case that they are wrong on the science.”

The CDC declined to comment, referring POLITICO to previous statements about the order as it applies to unaccompanied minors.

Title 42, once an obscure provision of U.S. health law, was first enacted by the Trump administration in the early days of the pandemic, and the Biden administration has continued to renew the order. So far, it has been used to turn away about 1.7 million individuals from the land border, the majority on President Joe Biden’s watch.

Immigration advocates and human rights groups argue that by not giving migrants arriving at the border the opportunity to claim asylum, the U.S. is failing to meet its obligations under international humanitarian law while at the same time projecting to be a moral leader of the West during Russia’s war with Ukraine.

The advocacy group Human Rights First says that there have been nearly 9,900 incidences of kidnapping, torture, rape and other attacks on people who have been expelled under Title 42 during the Biden administration alone.

“The idea that Title 42 is being kept in place for anything other than a purely political decision is preposterous at this point,” said Sergio Gonzales, executive director of the Immigration Hub, a national advocacy group. “How can we expect other countries in Europe to welcome refugees while keeping in place this terrible policy which completely undermines our country’s values?”

In March, the U.S. Court of Appeals for the D.C. Circuit upheld a lower court’s injunction in favor of families suing the U.S. government in a nationwide class action suit over its use of Title 42. The court said while the government had the right to expel migrants it considered a health threat during a public health emergency, it was unlawful for the government to expel people to countries where they might face persecution or torture.

The order remains in place until the Biden administration decides whether to appeal in late April, or end it sooner.

The judge noted that the federal government had failed to produce any current justification for Section 265 of the law, which allows the executive during a public health emergency to bar people from entering the country.

“This is March 2022, not March 2020,” Judge Justin Walker wrote. “The CDC’s 265 order looks in certain respects like a relic from an era with no vaccines, scarce testing, few therapeutics, and little certainty… We would be sensitive to declarations in the record by CDC officials testifying to the efficacy of the 265 Order. But there are none.”

Lee Gelernt, the ACLU lawyer who argued the case on behalf of the families, said the CDC did not put in an affidavit explaining why Title 42 was still necessary from a public health standpoint. “We suspect that the CDC does not think there is a public health justification any longer,” Gelernt said. “And that’s why they don’t want to put in an affidavit.”

CDC officials have not spoken at length publicly about Title 42. But in testimony released last fall, former CDC principal deputy director Anne Schuchat told lawmakers that most public health evidence didn’t support invoking the order when it was first put in place in 2020, and that a top CDC official in charge of border-related issues didn’t support using it.

On March 12, the CDC ended the order for unaccompanied noncitizen minors, having already stopped expelling that group early last year. A Texas court had issued a preliminary injunction stopping the agency from exempting unaccompanied children, questioning why it was treating them differently as a public health threat than adults and families.

In response, the agency said in a statement that “after considering current public health conditions and recent developments… expulsion of unaccompanied noncitizen children is not warranted to protect the public health.”

Ending the order for all migrants — minors, adults, and families alike — would be a major administrative, humanitarian and political challenge for the administration months before this year’s midterms.

On Thursday, Sen. Rick Scott (R-Fla.) and 13 other Republican senators sent a letter to Department of Homeland Security Security Alejandro Mayorkas demanding to know how the agency plans to “secure the border” if the administration ends Title 42.

“This is a grave concern that threatens to overwhelm our already strained immigration system and will only exacerbate a disastrous situation at our southern border,” the senators wrote.

Nevertheless, a growing number of Democratic lawmakers are calling for its end.

“It has never made sense to me as a public health policy,” Rep. Veronica Escobar (D-Texas,) told POLITICO. “We know that migrants who get rapidly expelled through Title 42 don’t stop trying to get in. They just make the attempt at a different place along the border… If what we’re worried about is [Covid-19] spread, that essentially creates greater spread.”

Others worry that the U.S. — and the CDC in particular — is losing its credibility by keeping it in place.

Dozens of epidemiologists, public health experts, and physicians have written a series of letters to the Trump and Biden administrations calling for an end to the expulsion order, but have not received any response from either, according to Monette Zard, director of the Forced Migration and Health Program at Columbia University and one of the letters’ signatories.

She is among those who are concerned about the message the CDC is sending to the world by allowing the order to continue.

“There must be a lot of soul searching going on [in the CDC],” Zard said. “It is deeply troubling to us that public health has been weaponized against such a vulnerable population. It certainly does nothing to advance the credibility of the CDC that it is allowing itself to be used in this way.”