Nebraska Attorney General Mike Hilgers is leading 21 other Republican state attorneys general in urging Congress to expand its investigation into improper influence on federal judges to include the Federal Judicial Center’s newly released Reference Manual on Scientific Evidence, which they argue is riddled with climate activism bias and threatens judicial impartiality.

In a letter sent to House Judiciary Committee Chairman Jim Jordan (R-Ohio), Subcommittee Chairman Darrell Issa (R-Calif.), and Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa), the attorneys general contend the 1,600-page manual, published December 31 with a foreword by Supreme Court Justice Elena Kagan—presents a “highly biased, agenda-driven view favoring radical interests pursuing lawsuits against producers and users of traditional forms of fossil fuel energy.”

The letter argues the latest edition embeds disputed, plaintiff-driven climate theories as settled science while failing to acknowledge competing scientific views or disclose conflicts of interest among contributors. The attorneys general point to extensive footnotes relying on left-leaning and climate-alarmist sources, including Columbia University climate advocate Jessica Wentz, climatologist Michael Mann, and attorneys actively representing cities suing energy companies.

“When the same advocates and experts who are actively litigating climate cases help write and review a chapter that will be used by federal judges behind the scenes, it raises obvious and serious concerns about the impartiality of the judicial system,” Hilgers said. “Nebraskans, and all Americans, deserve courts that are neutral and fair.”

The attorneys general also sent a separate letter to Federal Judicial Center Director Robin Rosenberg, criticizing what they described as a shift away from neutral scientific guidance toward placing the judiciary “firmly on one side of some of the most hotly disputed questions in current litigation.” They warned that using taxpayer funds to publish such material risks shaping legal outcomes rather than educating judges.

Signatories to the letter include the attorneys general of Alaska, Florida, West Virginia, Alabama, Kentucky, Arkansas, Georgia, Idaho, Indiana, Iowa, Kansas, Louisiana, Mississippi, Missouri, Montana, North Dakota, South Dakota, South Carolina, Texas, and Wyoming.

West Virginia Attorney General JB McCuskey told Fox News Digital the manual reflects “ridiculous legal warfare” driven by politically motivated groups using courts and “liberal justices” to advance a climate agenda. “We must protect our judicial system and its impartiality,” McCuskey said.

American Energy Institute CEO Jason Isaac called the climate chapter an abuse of taxpayer funds that embeds “plaintiff-driven climate alarmist theories,” while Alliance for Consumers President O.H. Skinner described the manual as “the woke lawfare playbook in action.”