In the thick of his argument defending President Donald Trump s travel ban earlier this week, a top lawyer for the Department of Justice was thrown a curveball from a dark period in American history.

Richard Paez, a judge on the U.S. Court of Appeals for the 9th Circuit, asked Jeffrey Wall, the acting solicitor general, if the governments case for the executive order banning travelers from six Muslim-majority countries resembled the legal justifications for the displacement and incarceration of Japanese-Americans during World War II.

Without addressing the question head-on, Wall rejected the comparison.

This case is not Korematsu , and if it were, I wouldnt be standing here and the United States would not be defending it, Wall proclaimed, alluding to the landmark Supreme Court ruling that upheld the conviction of Fred Korematsu, a California man who defied the military exclusion order that forcibly removed and effectively imprisoned 120,000 Japanese-Americans during the war. About two-thirds of those incarcerated were U.S. citizens, and many were children.

Justice Frank Murphy, one of the three justices who dissented in the 1944 Korematsu decision, likened his colleagues ruling to the legalization of racism .

The exchange was a marquee moment during this weeks court hearing one of two that could decide the fate of Trumps so-called Muslim ban. Trumps executive order hasnt been enforced since a pair of federal judges put it on hold after concluding that it was driven by unconstitutional animus against Muslims.