Buried in the April 2022 ruling that struck down the Biden administration’s mask mandate was a section that was unusual for a court decision.

The outcome itself was far from surprising. Places all over the country were dropping local mask requirements, and the judge hearing this case — a challenge to the federal mandate to mask on planes and other public transportation — was a conservative Trump appointee, U.S. District Judge Kathryn Kimball Mizelle for the Middle District of Florida. Mizelle ruled that the Centers for Disease Control and Prevention’s mask requirement overstepped the agency’s legal authority.

What was eye-catching was her explanation of why. In her ruling, Mizelle wrote she had consulted the Corpus of Historical American English, an academic search engine that returns examples of how words and phrases are used in select historical texts. Mizelle searched “sanitation,” a crucial word in the 1944 statute that authorizes the CDC to issue disease-prevention rules, and found it generally was used to describe the act of making something clean. “Wearing a mask,” she wrote, “cleans nothing.”

Searching large linguistic databases is a relatively new approach to judicial analysis called legal corpus linguistics. Although it has gained in popularity over the last decade, it is barely discussed outside of an enthusiastic group of right-wing conservative legal scholars. Which raises the question: How did this niche concept wind up driving such a consequential decision in the country’s health policy?

Now, new disclosures seen by HuffPost shed some light. Just weeks before she issued the ruling, Mizelle had discreetly attended an all-expenses-paid luxury trip from a conservative group whose primary mission is to persuade more federal judges to adopt the use of corpus linguistics. For five days, Mizelle and more than a dozen other federal judges listened to the leading proponents of corpus linguistics in the comfort of The Greenbrier, an ostentatious resort spread out over 11,000 acres of West Virginia hillside.

The newly formed group that picked up the tab, the Judicial Education Institute, received more than $1 million in startup funding from the billionaire libertarian Charles Koch’s network and DonorsTrust, a nonprofit that has funneled millions in anonymous donations to right-wing causes and has been dubbed “the dark money ATM of the conservative movement.”

Trump appointed Mizelle to the federal bench in late 2020 over objections from the American Bar Association that she had not been practicing law long enough to be qualified. A search of her other rulings found she had never previously applied corpus linguistics.

Neither Mizelle nor the Judicial Education Institute responded to requests for comment.

In response to the new disclosure, Sen. Sheldon Whitehouse (D-R.I.), a member of the Senate Judiciary Committee who chairs the subcommittee on federal courts and oversight, called for more disclosure surrounding when judges attend ideological educational retreats.

“The multi-pronged billionaire-funded scheme to influence the judiciary includes flying amenable judges to luxury resorts to bathe them in the latest fantastical right-wing legal theories,” he said in a statement to HuffPost. “At the very least, the public ought to know when judges are attending lavish ‘seminars’ promoting the agenda of partisan special interests. The Judicial Conference should take a close look at tightening its rules to ensure transparency around such junkets.”

Legal corpus linguistics is not inherently ideological. Nevertheless, as the right-wing legal movement increasingly insists that courts must interpret the law based on “history and tradition,” conservatives have seized on corpus linguistics as a useful source of legitimacy.

“History,” as described by the conservatives who dominate the federal courts these days, has an uncanny way of mirroring the political beliefs of the modern GOP on issues like gun laws, school prayer, organized labor and abortion rights. Corpus linguistics, the thinking goes, with its air of big data, offers a potential retort to the accusations that judges are simply cherry-picking their view of the past.

But skeptics argue that it’s just as easy for an ideologically motivated judge to cherry-pick results from a search engine.

“A lot of what legal corpus work tends to do is allow you to pick and choose your history,” Anya Bernstein, a professor studying legal interpretation at the University of Connecticut School of Law who has written critically of legal corpus linguistics, told HuffPost in March. “You pick and choose your corpus, you pick and choose what you’re putting into the software, you pick and choose your results.”

Corpus linguistics have popped up sporadically over the years, including in opinions written by Supreme Court Justice Clarence Thomas. Thomas’ former clerk, Thomas Lee, is one of the concept’s original pioneers.

But Mizelle’s ruling, and the resulting sea change in public health, may be the most resounding proof-of-concept to date.

Although legal scholars protested the ruling as odd — one professor interviewed by NPR said she probably wouldn’t accept that level of analysis from a law student — almost immediately, the Biden administration announced it would not enforce the mask mandate while it appealed her decision. An appeals court later declared her ruling moot because the administration ended the COVID-19 public health emergency and made no moves to enforce another mask mandate.

HuffPost first revealed the existence of these luxury trips and the Judicial Education Institute’s conservative political ties in March. When it launched in 2022, the group convened more than two dozen judges at The Greenbrier and at the exclusive ski resort of Deer Valley, Utah.

The story renewed scrutiny on the lack of rules to prevent overtly ideological groups from rewarding federal judges or trying to influence by mixing legal education with lavish accommodations and travel.

“With The Greenbrier and Deer Valley, they’re indoctrinating judges … by taking them to fancy, fancy, fancy resorts so that they can learn what they’re supposed to do,” Whitehouse said while discussing the story on MSNBC’s The Last Word.

Now, in addition to the group’s influence on the decision that brought an end to the mask mandate, new disclosures reveal the group has continued to convene federal judges at prime vacation destinations.

Last summer, at least a half-dozen judges flew with the group to Orlando, Florida. This February, the group returned to The Greenbrier, where it held its inaugural retreat in 2022.

The group also held two conferences in Washington, D.C., in March of 2023 and March of this year. Disclosures say DonorsTrust provided funding for both the February 2024 Greenbrier retreat and the March 2024 D.C. retreat.