A new lawsuit by the Cato Institute could answer the question of whether the Supreme Court was wrong to accept assertions from former President Trump that his 2017 travel ban was based on security concerns, not animus against Muslims. Despite rescinding the ban, President Biden has still refused to disclose documents that Trump told the Court were the basis of his decision to ban immigrants from certain majority Muslim countries.

In a 5–4 decision, the Court’s majority found that the ban was based not on Trump’s open animus against Muslims, but instead on a Department of Homeland Security (DHS) report that supposedly detailed national security concerns. But the majority simply accepted this report as legitimate without ever seeing it. Indeed, DHS has allowed no one outside the Executive branch to see it.

After President Biden rescinded the ban—which he called “discriminatory”—I filed a Freedom of Information Act (FOIA) request on behalf of the Cato Institute for the DHS report. DHS ignored it, so now Cato is suing. It will be the first time Biden’s DHS will have to either justify keeping the report a secret from the public or else release it. Even if DHS refuses to release the report, the court can order it to do so.

Given that DHS’s new leadership labeled the ban “cruel” and “harmful,” DHS should have been forthcoming with the report that purportedly supported it. But not so far. DHS initially claimed not to be able to find the report. Cato appealed that determination and won, which should have forced DHS officials to look again. They chose not to, so now they will face Cato in court.

DHS has not said why it has not released the report, but it shouldn’t worry about being blamed for misleading the Supreme Court. The blame will fall exactly where it should: on Donald J. Trump. Lest anyone forget, it was Trump who instigated the Muslim ban. It was Trump who, in his words, “morphed” it into a ban on select majority-Muslim countries so he could blunt a constitutional challenge.

How did the Supreme Court ignore this back story and uphold the ban as constitutional? First, it adopted a laughably low bar, the so-called “rational basis test” under which courts would have accepted nearly any justification except perhaps for the one Trump stated initially: “Islam hates us.” And where did Trump find a suitable replacement for his initial justification? From the DHS report that the department still refuses to disclose.

The most discriminatory executive action taken against immigrants by any U.S. president, the Court’s opinion asserted, “reflects the results of a worldwide review.” The ban was purportedly “based on [the President’s] findings—following a worldwide, multi-agency review—that entry of the covered aliens would be detrimental to the national interest.” The justices refer to this review or report at least 16 times in their majority and dissenting opinions.

According to former President Trump, the DHS report reviewed the adequacy of the local vetting systems “in more than 200 countries.” DHS came up with a set of baseline requirements that every country must implement (e.g., having electronic passports), and then it purportedly compared each country against this baseline, banning those that failed the baseline requirements.

In response to a question by Justice Sotomayor during oral argument, Solicitor General Noel assured the Court that the president’s personal feelings had no effect on the process because DHS was able “to construct and apply this neutral standard to every country in the world.” In other words, the ban was just an objective application of neutral security criteria, not a fulfillment of Trump’s discriminatory campaign promise.

But the Supreme Court never verified that the DHS report did any of this, and we have at least two very good reasons to doubt the claim’s veracity. First, President Trump’s proclamation identifying the banned countries lists the nine baseline criteria that DHS’s report supposedly applied equally to every country. Under a neutral application of those criteria, however, dozens of other countries—including many non-Muslim countries—should have failed.

Second, although the justices never saw the actual report, they did know that it was just 17 pages. Did DHS analyze the vetting systems of more than 200 countries in 17 pages across nine security metrics as the president claimed? It certainly did not. Yet the majority justices said that they it would not question DHS’s “thoroughness” because “a simple page count offers little insight into the actual substance of the final report”—the very substance that DHS has sought to hide and Cato’s lawsuit now seeks to uncover.

This is not the first FOIA request DHS has rebuffed on this subject. When the Brennan Center in New York requested the same document in 2017, DHS acknowledged that it existed and was 17 pages. But the department asserted that the report was confidential and exempt from FOIA disclosure. To date, no court has issued a final decision in that case, and the Biden administration has never been made to respond to it. More importantly, now that it has repudiated the ban, DHS has no legitimate reason to continue hiding the requested documents.

If Donald Trump were to become president again, the Muslim ban could be quickly reimposed. Without the benefit of the report, no one challenging the ban—politically or legally—would be able to completely discredit the justification that Trump gave the court last time. DHS should reveal whether the former President misled the Supreme Court and, if so, how he did it, before it’s too late.