The Trump administration's move to lift restrictions on the indefinite detention of immigrant families is unlikely to survive anticipated legal challenges, if courts agree with immigrant advocates that it violates a decades-old agreement, constitutional due process and administrative law.

Although acting Homeland Security Secretary Kevin McAleenan defended the final rule, announced Wednesday, as one that ensures the safety and well-being of children, a California federal judge presiding over a case challenging a draft of the rule is expected to find the final version inconsistent with a 1997 federal consent decree known as the Flores settlement agreement, which established bedrock standards of care for migrant children.

The rule would allow minors to be detained on a prolonged basis, which has been shown to cause lasting mental and physical harm, and while the text of the rule has yet to be released, it could be seen as the government trying to shirk its responsibilities to the care of migrant children, according to Elyse Echtman, a partner at Orrick Herrington & Sutcliffe LLP who is working on the enforcement of the settlement.

"If they're trying to materially change their obligations, they're not allowed to do that," she said. "To the extent that the regs are not consistent with the agreement, we will be challenging them."

Echtman and other Flores counsel already filed a brief before U.S. District Judge Dolly Gee in November asking her to hold the government in civil contempt of the settlement agreement based on the proposed version of the rule, but the judge said she would defer ruling until the final rule was published. Assuming there are no major changes in the final text, that brief might be a "nice starting place" for their case against the rule, Holly Cooper, another attorney on the case, tweeted Wednesday.

In that brief, they argued that the proposed rule is "wholly inconsistent" with provisions of the settlement requiring that children be swiftly released from detention if they are likely to show up for their immigration court hearings and detention is not necessary to ensure their safety or that of others. The settlement puts a hard 20-day limit, backed by organizations such as the American Psychological Association and the American Academy of Pediatrics, on the time that immigrant children can safely spend in detention.

At the core of Flores is the idea that "children don't belong in jail," and any attempt to extend the time period children can be detained or to keep them in jail-like settings would therefore violate the settlement, Echtman said. 

Echtman said that courts have recently seemed to uphold that idea, with the Ninth Circuit ruling last week that U.S. Customs and Border Protection had violated the settlement by failing to provide basic hygiene products, nutrition and adequate sleeping accommodations to immigrant children in its custody. In that case, a three-judge panel rejected the government's contention that it should not have to provide what it deems to be nonessential amenities that are not specifically mentioned in the settlement agreement to children in detention.

House Speaker Nancy Pelosi expressed optimism Wednesday that Judge Gee would similarly reject the government's notion that indefinitely detaining children abides by the Flores settlement.

"This inhumane and utterly unconscionable rule circumvents the conditions set in the Flores settlement, and we expect the district court to swiftly strike it down," she said in a statement.

It is possible that independent suits challenging the rule will be filed.

Stephen Yale-Loehr, a professor at Cornell Law School, said courts might find the rule to be an "arbitrary and capricious" agency action under the Administrative Procedure Act because it fails to abide by the spirit of the Flores agreement. Numerous other challenges to Trump administration immigration policies — such as its decision to rescind deportation protection for hundreds of thousands of young immigrants in the Deferred Action for Childhood Arrivals program — have succeeded on APA grounds.

Legal challenges might also raise constitutional due process claims. The U.S. Supreme Court has held that holding immigrants for prolonged periods raises due process concerns, Shoba Wadhia, a professor at Penn State Law, noted.

Refugees International's Yael Schacher said that due process concerns would also arise if the rule were found to use detention as a deterrent to seeking asylum.

"Under U.S. law, immigration detention is not supposed to be a deterrent, nor did it prove an effective one before the July 2015 federal court ruling confirming the Flores settlement," Schacher said in a statement. "More fundamentally, seeking asylum at the border is not a crime and immigration detention is not supposed to be a punishment."

Lawsuits might also challenge the conditions of detention.

McAleenan claimed Wednesday that family detention centers have a "campus-like setting" where families are housed in separate suites, children attend school five days a week, and there are three hot meals daily, as well as a medical wing and many recreational opportunities. But even the Department of Homeland Security's internal watchdog has told a different story, reporting serious overcrowding and lack of proper nutrition at Texas family detention facilities.

"My experience in immigration and family detention is sharply different from the resort-like picture painted by DHS when announcing the forthcoming rule," Wadhia said. "If the treatment of children by DHS this summer and exposed in the media and on the Hill is any indication for how DHS may treat families and children in the wake of this new rule, we can expect a litany of legal challenges."

--Editing by Aaron Pelc.