The Trump administration defended the executive order as a lawful exercise of the president’s immigration powers to bolster national security, an argument that usually receives broad deference from the courts. “This debate should go back to where it belongs: the political realm,” acting Solicitor General Jeffrey Wall told the court. But critics like the state of Hawaii, which filed the lawsuit on behalf of its university system and its foreign-born residents, argue instead that the order is aimed at fulfilling Trump’s discriminatory campaign pledge to stop Muslim immigration.

Looming over Monday’s arguments was Korematsu v. United States, the infamous Supreme Court case in which the justices upheld Franklin D. Roosevelt’s executive order on Japanese-American internment during World War II. At one point, Wall urged the panel to rely on the legal standard articulated in Kleindienst v. Mandel, a 1972 Supreme Court case. In Mandel, the Court ruled that immigration-related decisions by the executive branch need only a “facially legitimate and bona fide reason” to survive judicial scrutiny. That ruling established a low threshold for future presidents to overcome in immigration cases; in this one, national-security concerns cleared the threshold, the federal government has argued.

When Judge Paez asked Wall whether Korematsu would hypothetically survive under the Mandel standard, Wall disputed the question’s premise. “I want to be very clear about this: This case is not Korematsu. And if it were, I wouldn’t be standing here and the United States would not be defending it,” he added, using the country as a legal metonym for the solicitor general’s office.

Katyal, a former acting solicitor general who in 2011 effectively recanted his predecessors’ defense of internment, found the historical resonance inescapable. “As Justice [Robert H.] Jackson said in the context of the First Amendment in a religious-freedom case, ‘The First Amendment was designed to avoid these ends by avoiding these beginnings,’” he told the panel in his closing remarks. “This very courthouse, which tried, convicted, and then later exonerated Gordon Hirabayashi 44 years ago, stands as a physical reminder about what is at stake.” Hirabayashi unsuccessfully challenged the constitutionality of a curfew for Japanese-Americans during World War II.

Hawaii v. Trump is one of multiple legal challenges against the second iteration of Trump’s executive order, which temporarily bars visa applications from six Muslim-majority countries and suspends the U.S. Refugee Admissions Program for 120 days. Trump signed the revised executive order in March, but Watson issued an injunction blocking it from going into effect. The Trump administration appealed the injunction to Monday’s Ninth Circuit panel.

This isn’t the administration’s first bout in the Ninth Circuit, which covers most of the western United States. Trump’s initial iteration of the travel ban prompted a frenzy of lawsuits in the chaotic weekend following its haphazard rollout in January. Multiple federal judges, including James Robart in Seattle, temporarily blocked the administration from implementing the executive order while the legal process unfolded. The federal government then appealed Robart’s injunction in Washington v. Trump to a three-judge Ninth Circuit panel in February, which unanimously upheld Robart’s ruling. The Trump administration opted then to rewrite the executive order instead of asking the Supreme Court to intervene.