The U.S. Supreme Court on Monday allowed Donald Trump to pursue deportations of alleged Venezuelan gang members using a 1798 law that historically has been employed only in wartime as part of the Republican president's hardline approach to immigration, but with certain limits.

The court, in an unsigned 5-4 ruling powered by conservative justices, granted the administration's request to lift Washington-based U.S. Judge James Boasberg's March 15 order that had temporarily blocked the summary deportations under Trump's invocation of the Alien Enemies Act while litigation in the case continues.

Despite siding with the administration, the court's majority placed limits on how deportations may occur, emphasizing that judicial review is required.

Detainees "must receive notice after the date of this order that they are subject to removal under the Act. The notice must be afforded within a reasonable time and in such a manner as will allow them to actually seek habeas relief in the proper venue before such removal occurs," the majority wrote.

The court has a 6-3 conservative majority. Conservative Justice Amy Coney Barrett and the court's three liberal justices dissented.

Trump's administration has argued that Boasberg had encroached on presidential authority to make national security decisions.

"The Supreme Court has upheld the Rule of Law in our Nation by allowing a President, whoever that may be, to be able to secure our Borders, and protect our families and our Country, itself," Trump wrote on social media.

Trump invoked the Alien Enemies Act on March 15 to swiftly deport the alleged members of the Tren de Aragua gang, attempting to speed up removals with a law best known for its use to intern Japanese, Italian and German immigrants during World War Two.

In Monday's decision, the court said that to challenge the legitimacy of their detention under the Alien Enemies Act detainees must pursue so-called habeas corpus claims in the federal judicial district where a detainee is located. That means that the proper venue for this litigation was in Texas, not the District of Columbia, the court said.

The ruling said the court was not resolving the validity of the administration's reliance on that law to carry out the deportations.

The plaintiffs in the case "challenge the government's interpretation of the Act and assert that they do not fall within the category of removable alien enemies. But we do not reach those arguments," the court decided.

In a legal challenge handled by the American Civil Liberties Union, a group of Venezuelan men in the custody of U.S. immigration authorities sued on behalf of themselves and others similarly situated, seeking to block the deportations. They argued, among other things, that Trump's order exceeded his powers because the Alien Enemies Act authorizes removals only when war has been declared or the United States has been invaded.

The law authorizes the president to deport, detain or place restrictions on individuals whose primary allegiance is to a foreign power and who might pose a national security risk in wartime.

DUE PROCESS

Lee Gelernt, a lawyer with ACLU and lead counsel representing the detainees, framed the court's decision as a win for his side.

"This ruling means we will need to start the court process over again in a different venue, but the critical point is that the Supreme Court said individuals must be given due process to challenge their removal under the Alien Enemies Act," Gelernt said. "That is a huge victory."

The dissenting justices, in an opinion written by liberal Justice Sonia Sotomayor, criticized the majority's "dubious" conclusions in the case and for acting with just a few days of deliberation.

There is "every reason to question the majority's hurried conclusion that habeas relief supplies the exclusive means to challenge removal under the Alien Enemies Act," Sotomayor wrote.

Sotomayor said that federal courts called upon to review these cases going forward will probe the interpretation of the Alien Enemies Act, including whether there is an "invasion" or "predatory incursion" justifying its use, and "whether any given individual is in fact a member of Tren de Aragua."

Requiring detainees to make individual claims across the country "risks exposing them to severe and irreparable harm," Sotomayor wrote in part of the dissent joined by the two other liberal justices and not Barrett. One risk is that they will not know whether they will remain in detention where they are arrested or be secretly transferred to an alternative location, Sotomayor said.

"That requirement may have life or death consequences," Sotomayor wrote.

Boasberg, an appointee of Democratic President Barack Obama, temporarily blocked the deportations. But Trump's administration allowed two planes already in the air to continue to El Salvador where American officials handed 238 Venezuelan men over to Salvadoran authorities to be placed in the Central American country's "Terrorism Confinement Center."

The judge also has scrutinized whether the Trump administration violated his order by failing to return the deportation flights after his order was issued. Justice Department lawyers said the flights had left U.S. airspace by the time Boasberg issued a written order and thus were not required to return. They dismissed the weight of Boasberg's spoken order during a hearing two hours earlier calling for any planes carrying deportees to be turned around.

On March 18, Trump called for Boasberg's impeachment by Congress - a process that could remove him from the bench - drawing a rebuke from the U.S. Chief Justice John Roberts. Trump on social media called Boasberg, who was confirmed by the U.S. Senate in 2011 in a bipartisan 96-0 vote, a "Radical Left Lunatic" and a "troublemaker and agitator."

Monday's decision was the latest in recent days in which the Supreme Court sided with Trump. In a 5-4 decision on Friday, it let Trump's administration proceed with millions of dollars of cuts to teacher training grants - part of his crackdown on diversity, equity and inclusion initiatives. The court earlier on Monday also temporarily halted a judge's order requiring the administration to return by the end of the day a Salvadoran man who the government has acknowledged was deported in error to El Salvador.