The 9th Circuit Court of Appeals on Friday suspended an order issued earlier in the day that blocked the Remain-in-Mexico policy -- the cornerstone of the Trump administration's efforts in curbing the crisis at the southern border.

The panel in San Francisco had ruled in a 2-1 vote to put a hold on the policy -- formally known as the Migrant Protection Protocols (MPP). But it later voted to suspend the order and told the government to file written arguments by the end of Monday and for the plaintiffs to respond by the end of Tuesday.

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"This evening, with support of DOJ attorneys and CBP’s declaration, the 9th Circuit granted a stay of its earlier order enjoining MPP," Customs of Border Protection (CBP) Acting Commissioner Mark Morgan tweeted. "@CBP will immediately reinstate MPP!"

The policy, which was established in January and expanded over the summer amid greater cooperation with Mexico, returns migrants seeking asylum to Mexico as they await their hearings, with courtrooms set up at key border points.

The policy was key in ending the process known as “catch-and-release” by which migrants were released into the interior, sometimes for years, until their cases were processed. It was identified as a key “pull factor” in why migrants were flooding the border.

Officials said the process meant that cases could be heard in as little as 40-60 days, as opposed to the years it sometimes takes after family units are released into the U.S. Those in favor of the program said that works better for the migrants, as it leaves them in limbo for less time, while also acting as a disincentive for Central American migrants who do not have legitimate asylum claims but might otherwise get into the U.S. by claiming “credible fear” of returning home.

But the 9th Circuit accepted arguments that returning migrants to Mexico put them at risk of violence and kidnapping, saying not enough was done to protect them from harm. Civil rights groups have called the policy "secretive" and part of an attack on legitimate asylum claims. Multiple 2020 Democratic presidential hopefuls have promised to end the policy if elected to the White House.

Since MPP was expanded, there has been a dramatic drop in migrants coming to the border. Officials have repeatedly said the policy, along with other international agreements with Central American countries, has been a significant factor in that reduction. About 60,000 migrants had been returned to Mexico under the protocols.

The Justice Department had said Friday that at least 25,000 asylum seekers subject to the policy are currently waiting in Mexico and expressed “massive and irreparable national-security of public-safety concerns" if it was halted.

Attorneys said immigration lawyers had begun demanding that asylum seekers be allowed in the United States, with one insisting that 1,000 people be allowed to enter at one location.

“The Court’s reinstatement of the injunction causes the United States public and the government significant and irreparable harms — to border security, public safety, public health, and diplomatic relations,” Justice Department attorneys wrote.

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ACLU attorney Judy Rabinovitz called the suspension of Friday's order "a temporary step."

“We will continue working to permanently end this unspeakably cruel policy,” she said.

The government could appeal the case up to the Supreme Court where the government has been racking up wins on the subject of immigration. Officials are in broad agreement on the importance of MPP if the crisis at the southern border is going to be prevented from flaring up once again as it did a year ago, when 144,000 migrants reached the border in April.

“The importance of MPP can’t be stated enough, it is what’s allowed us to take control of the crisis that we saw in April and May. The idea is to make sure we process individuals in a timely manner but make sure they wait south of the border,” Acting Homeland Security Secretary Chad Wolf told Fox News in November.

Wolf warned then that a ruling by the Ninth Circuit could have a dire effect on the U.S. effort to regain control of its southern border.

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“So you get an adverse ruling on MPP and it’s going to make the job of the men and women of Border Patrol as well as [Customs and Border Protection] and [Immigration and Customs Enforcement] ... very difficult for them, so it really can’t be overstated how much the program means to the department in controlling the crisis,” he said.

The Associated Press reported that on Friday the liberal group Human Rights First hand-delivered a copy to CBP officers at a bridge connecting Laredo, Texas, and Nuevo Laredo, Mexico. Lawyers were hoping to get their clients before U.S. immigration court judges.

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The Justice Department sharply criticized the ruling, saying it “not only ignores the constitutional authority of Congress and the administration for a policy in effect for over a year, but also extends relief beyond the parties before the court.” Wolf called the decision “grave and reckless.”

The Associated Press contributed to this report.