This seems to confirm my suspicions:
>>>Stephen Miller, the main architect of Mr. Trump’s domestic agenda, had a message for other advisers inside the presidential transition offices in West Palm Beach, Fla.: Be bold. Do not worry about potential litigation, especially when drafting Mr. Trump’s immigration actions. . . .
Mr. Miller had long been interested in the Alien Enemies Act, a law passed in 1798 that allows the U.S. government to swiftly deport citizens of an invading nation. . . .He saw it as a powerful weapon to apply to immigration enforcement.
The law “allows you to instantaneously remove any noncitizen foreigner from an invading country, aged 14 or older,” Mr. Miller told the right-wing podcaster Charlie Kirk
in a September 2023 interview, adding: “
That allows you to suspend the due process that normally applies to a removal proceeding.”<<< (emphasis added)
New details deepen questions about the deportations, showing that El Salvador’s president pressed for assurances that the migrants were really members of the Tren de Aragua gang.
www.nytimes.com
Mr Miller: Please read the United States Constitution, including the 5th amendment.
It's mind-boggling that Trump is apparently relying on legal advice from someone with no knowledge of the law.
In terms of the MS-13 gang members, this provides some insight:
>>>Mr. Bukele had his own request: a list of MS-13 leaders that he wanted released from U.S. custody and sent to El Salvador, where he said they could be interrogated by his security officers. . . .
“What Bukele is desperate for is to get these guys back in El Salvador before they talk in U.S. court,” said Douglas Farah, an El Salvador expert who between 2018 and 2022 collaborated with the Justice Department “Vulcan” task force, which targeted MS-13, as a U.S. military contractor.<<< (emphasis added)
I strongly suspect the administration invoked the state secrets doctrine in an effort to keep embarrassing facts hidden, not for legitimate reasons related to national security. It smells like desperation born from the realization that "Oh sh*t, we F'd up, now what?!?"