– "I'm calling, very simply, for a shutdown of Muslims entering the United States," Donald Trump said on Dec. 8, 2015. It was early in his presidential campaign, and he was saying that sort of thing all the time.

On this occasion, though, he also cited a historical precedent. "Take a look at what FDR did many years ago," Trump said. "He did the same thing."

President Franklin D. Roosevelt signed a 1942 executive order that sent more than 110,000 people of Japanese ancestry to internment camps.

"This is a president who was highly respected by all," Trump said of Roosevelt. "They named highways after him."

Next week, the Supreme Court will hear arguments in a challenge to Trump's executive order, one that restricted travel from eight nations, six of them predominantly Muslim. It is the last scheduled argument of a busy term, and it is likely to yield a major statement on presidential power.

The justices will consider how much weight to give to Trump's campaign statements. And they will act in the shadow of their own 1944 decision in Korematsu vs. United States, which endorsed Roosevelt's 1942 order and is almost universally viewed as a shameful mistake.

The Justice Department has worked hard to limit the damage from Trump's campaign statements, which were often extemporaneous and rambling. It was hard to tell, for instance, precisely which Roosevelt policies Trump referred to or endorsed in his 2015 remarks.

"Impugning the official objective of a formal national security and foreign policy judgment of the president based on campaign trail statements is inappropriate and fraught with intractable difficulties," Solicitor General Noel Francisco told the justices in a brief filed in February.

The challengers — Hawaii, several individuals and a Muslim group — took a different view. Trump's order, they said, was "the fulfillment of the president's promise to prohibit Muslim immigration to the United States."

A pair of supporting briefs, from children of Japanese-Americans held in the detention camps and several public interest groups, went further. They said Trump's latest travel ban is of a piece with Roosevelt's order.

"History teaches caution and skepticism when vague notions of national security are used to justify vast, unprecedented exclusionary measures that target disfavored classes," lawyers for the Japanese American Citizens League told the justices.

There are, of course, major differences between the two orders, as legal scholars have noted. Roosevelt's order applied to people living in the United States, many of them citizens, while Trump's order concerned nationals of other countries living abroad. (The countries initially included Iran, Libya, Syria, Yemen, Somalia, Chad, North Korea and Venezuela. Last week, the administration lifted restrictions on travel from Chad.)

In enforcing Roosevelt's order, moreover, the military singled out "persons of Japanese ancestry." Trump's order, by contrast, is neutral on its face, though it disproportionately affects Muslims.

Still, the legacy of the Korematsu decision figured in opinions in recent appeals court decisions blocking Trump's third and most considered travel ban, issued as a presidential proclamation in September.

The Korematsu decision occupies a curious place in the Supreme Court's jurisprudence, as a grave error that has never been formally disavowed. Justice Antonin Scalia wrote that Korematsu ranks with Dred Scott, the 1857 decision that black slaves were property and not citizens, as among the court's most disastrous rulings.

In 1982, a congressional commission concluded that the internment of Japanese-Americans was "a grave injustice" animated by "race prejudice, war hysteria and a failure of political leadership." It added that "the decision in Korematsu lies overruled in the court of history."

But the Supreme Court has never overruled the decision. It remains, in the words of Justice Robert Jackson's dissent, "a loaded weapon, ready for the hand of any authority that can bring forward a plausible claim of an urgent need."