Is the 226-year-old Alien Enemies Act going to pass muster at the Supreme Court? The last time the court weighed the rarely-used law, in 1948, the Nine by five to four vindicated the president’s authority to use the law to expel a German national. Now that the law has been lifted from obscurity by President Trump, who invoked it to deport some 200 aliens on Sunday, the measure could return to the high court. 

Mr. Trump’s use of the venerable law comes as no surprise. It was a plank in his winning presidential platform. He vowed at one rally to “invoke the Alien Enemies Act of 1798 to target and dismantle every migrant criminal network operating on American soil.” In Arizona, he touted the law, noting “Those were the old days, when they had tough politicians.” He added: “Think of that, 1798. Oh, it’s a powerful act. You couldn’t pass something like that today.”