A group of 50 House Democrats signed a letter on Wednesday asking Justice Clarence Thomas to recuse himself from a major Supreme Court case that could dramatically alter federal agencies’ powers.

The latest report from the nonprofit Propublica outlet revealed that Thomas has been a guest at more than one event hosted by the conservative Koch network, including a dinner for donors at its annual summit in California in 2018.

Rep. Dan Goldman (D-N.Y.) led the initiative calling on Thomas’s recusal, arguing attorneys involved in the Loper Bright Enterprises v. Raimondo case are staff members for the Koch network.

“There is no question that your lengthy relationship with the Kochs, including your par

Associate Justice Clarence Thomas

ticipation in donor retreats for the Koch network, requires recusal in the upcoming case that the Koch network has teed up in an attempt to overturn Chevron,” the lawmakers wrote.

“Moreover, as you should be aware, the Koch network’s staff attorneys represent the plaintiffs in this

case.”

The oral arguments in the case surround the long-standing precedent known as the Chevron deference, which tells courts to defer to a federal agency’s reasonable interpretation of laws enacted by Congress and the president, even though many are written ambiguously.