The Alien Enemy Act is actually an incredibly old law (i.e., it’s not a new development). What is new is attempting to use it based on a declaration that there’s been a non-military invasion ( https://www.congress.gov/crs-product/LSB11269 ). I think it’s pretty clear that the Supreme Court is going to eventually strike that down, but the courts can only act in response to the cases they get, and only answer specific legal questions at different phases of those cases.

But about a month ago, the Court did rule people who the government wanted to send to El Salvador have a due process right to challenge that decision in regular federal court as a habeas corpus proceeding ( https://www.supremecourt.gov/opinions/24pdf/24a931_2c83.pdf ). They later issued an order that the people covered by the original ruling cannot be deported based on the Alien Enemy Act until further notice ( https://www.supremecourt.gov/orders/courtorders/041925zr_c18... ).