In late February, during his address to a Joint Session of Congress, President Trump claimed, that, “according to data provided by the Department of Justice, the vast majority of individuals convicted of terrorism and terrorism-related offense since 9/11 came here from outside of our country.”

A week later, in the revised Executive Order restricting entry from six countries, the administration declared that, “Since 2001, hundreds of persons born abroad have been convicted of terrorism-related crimes in the United States.”

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Another thing happened around the same time: A new, more comprehensive dataset became available to the public. Shirin Sinnar at Stanford Law School received under a Freedom of Information Act request from 2015 the National Security Division’s list of public and unsealed international terrorism and terrorism-related convictions from September 11, 2001 to December 31, 2015. Writing at Just Security, she pointed out that this list had previously been provided in early 2015 to the Senate Subcommittee on Immigration and National Interest, chaired at the time by none other than then Senator Jeff Sessions. The subcommittee had conducted its own open-source research on the immigration status of each defendant and the results were published in February 2017 by the Center for Immigration Studies, a group that favors lower immigration numbers. Fox News and Stephen Miller ran with CIS’s headline: “Study Reveals 72 Terrorists Came from Countries Covered by Trump Vetting Order,” while the Washington Post fact-checked the study. The Post noted that some of the individuals on the list had entered the United States years before they conducted any crime and many of those individuals were not bomb makers, they engaged in more innocuous activities such as transferring money.

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This inquiry was labor intensive because the Justice Department’s list does not include material about the country of origin of terrorist defendants—we suspect because the Justice Department may not actually keep or have such data, which generally are not relevant to the criminality of the suspects. Whether there exist internal data within the Justice Department that supports the President’s claim we do not purport to know. But if such data do exist, as we will show, they would have to be quite different from the list of cases NSD released in response to Sinnar’s FOIA request.

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It’s important to emphasize that the bounds of the dataset here artificially inflate the percentage of foreign-born subjects. In other words, the very dataset we’re consulting is the one most apt to support the administration’s position. As Sinnar pointed out, the list doesn’t include any individuals convicted of domestic terrorism offenses; the Justice Department only released the names of individuals who were convicted of international terrorism offenses; these individuals are dramatically more likely to be foreign born than people convicted of domestic terrorism crimes. Consequently, Sinnar noted, we can only draw limited conclusions from the dataset: “If you exclude all convictions for ‘domestic terrorism’ at the outset, how can you draw any overall conclusions on the citizenship status or national origin of those convicted of terrorism?”