In a stunning escalation, the Trump administration announced Wednesday that it will abrogate a decades-old legal agreement in order to indefinitely detain immigrant families.

The proposed termination of what’s known as the Flores agreement is President Donald Trump’s most aggressive—and most legally suspect—attempt to circumvent legal protections for undocumented children since his disastrous “zero-tolerance” policy resulted in the separation of thousands of immigrant families.

“No child should be a pawn in a scheme to manipulate our immigration system,” Acting Secretary of Homeland Security Kevin McAleenan told reporters in a press conference Wednesday morning. “This action by the administration is just one part of our overall effort, but it’s an essential one.”

Under the new regulations, set to go into effect 60 days from this Friday pending the approval of a federal judge, the Trump administration would formally abolish the Flores agreement’s key standard of care: a 20-day limit on holding children in immigration detention. While McAleenan stated that “there is no intent to hold families for a long period of time,” the rule change would allow for families to be held in detention indefinitely, pending a final ruling on their case.

The Daily Caller first reported the impending changes to the agreement on Tuesday evening, quoting a senior administration official as saying that “today the administration is closing one of the legal loopholes that has allowed human traffickers and smugglers to exploit our vulnerabilities at the southern border.”

Ending the agreement, the official continued, “plays a vital role in the strategy to restore the integrity to our immigration system and our national security.”

Named for 15-year-old Jenny Lisette Flores, who fled El Salvador in the 1980s and was detained among adults in dangerous conditions by the Immigration and Naturalization Services—and not for a “Judge Flores,” as Trump once claimed—the agreement created stringent standards regarding the detention and release of undocumented children in U.S. government custody. Most notably, the federal government is required to release children into the custody of licensed care programs within 20 days, as well as to place children in the least restrictive setting possible, with access to sanitary facilities, medical treatment, and contact with family members.

McAleenan declared that while the government currently only has between 2,500 and 3,000 beds available for holding families—for context, roughly 107,000 family units were apprehended while attempting to enter the United States in Fiscal Year 2018—the settings will be “campus-like” in nature, with libraries, schools, and assurances that kids will be “well cared for.”

But pediatricians, child welfare advocates and immigration attorneys have well-founded fears that this will not be the case. Six children have died in immigration custody in the past eight months, and healthcare experts have told The Daily Beast that no length of detention is safe for children.

“The conditions to which he was subject are not supportive of recovery, and also, because of the stress of the experience, place children at very high risk for infectious diseases,” said Dr. Julie Linton, co-chair of the American Academy of Pediatrics Immigrant Health Special Interest Group and a practicing pediatrician. “When children are sick, exposure to stress hormones makes it much more difficult to recover from illness.”

The Flores agreement has long been one of the highest barriers to Trump’s immigration agenda, particularly in the context of the administration’s family separation policy. Trump and administration officials pointed to the FSA as the reason behind family separation, with then-White House press secretary Sarah Huckabee Sanders telling reporters in June that “the separation of illegal alien families is the product of the same legal loopholes that Democrats refuse to close, and these laws are the same that have been on the books for over a decade.”

The Trump administration has supported legislation that would make it easier to hold children indefinitely, and has brazenly flouted many of the Flores agreement’s key stipulations, including holding undocumented minors for weeks longer than the 20-day maximum, arguing that the Flores only applies to unaccompanied children, rather than those who arrived at the U.S. border with family members. (A federal appellate court ruled in 2016 that Flores applies to all minors, unaccompanied and otherwise.)

In September 2018, the Trump administration floated a potential rule change that would allow for the long-term detention of immigrant children and families by allowing the federal government to license detention centers run by Immigration and Customs Enforcement as suitable for the long-term detention of children. The FSA requires that children be released after 20 days into the custody of state-licensed residential facilities—the proposal would instead give that licensing authority to the federal government.

“Today, legal loopholes significantly hinder the department’s ability to appropriately detain and promptly remove family units that have no legal basis to remain in the country,” then-Homeland Security Secretary Kirstjen Nielsen said in a statement at the time. “This rule addresses one of the primary pull factors for illegal immigration and allows the federal government to enforce immigration laws as passed by Congress.”

After the plan was first crafted, the Department of Homeland Security punted on the proposal, instead asking Congress to re-work Flores.

Like many of the Trump administration’s other attempts to weaken legal protections for immigrants, McAleenan admitted that decision to change the FSA to allow for the indefinite detention of families will almost certainly be met with legal challenges from advocacy organizations.

“We do expect litigation,” McAleenan said.

Madhuri Grewal, policy counsel for the American Civil Liberties Union, nearly guaranteed a legal challenge in a statement released following the official announcement.

“This is yet another cruel attack on children, who the Trump administration has targeted again and again with its anti-immigrant policies,” Grewal said. “The government should not be jailing kids, and certainly shouldn’t be seeking to put more kids in jail for longer. Congress must not fund this.”

Other advocacy organizations were more succinct in their reaction to the administration’s plan. The Refugee and Immigrant Center for Education and Legal Services tweeted on Wednesday: “It’s cruel beyond imagination.”