The federal appeals court overseeing a challenge to the Biden administration’s $8 cap on credit card late fees wants to hear arguments about whether a judge with stock holdings in the nation’s second-biggest credit card lender should continue to hear the case.

The 5th U.S. Circuit Court of Appeals on Monday night asked both sides — the Consumer Financial Protection Bureau and the industry groups challenging the fee limits — to submit briefs about whether a judge’s ownership interest in a large credit card issuer “would be substantially affected by the outcome of this litigation.”

The request came after POLITICO reported earlier Monday that one of the judges hearing the case, Don Willett, had disclosed stock holdings in Citigroup.

Citi and other lenders collectively stand to lose billions of dollars in fee revenue if the CFPB’s rule survives.

Willett’s most recent financial disclosure report in May 2023 listed Citi shares in two separate accounts with each holding valued at $15,000 or less at the end of 2022.

In a statement on Tuesday, Willett said that some Citi shares were owned through a Coverdell Education Savings Account for one of his children and worth “about $2,000.“ He added that another child “had a similar account but recently sold his Citigroup shares, also worth around $2,000, to help pay for school.“

The appeals court’s Monday night letter notes that a possible recusal question centers on “not the size of the interest but rather whether the interest could be substantially affected” by the outcome of the case.

The court said it wants briefs on the issue by the close of business on Thursday.

Willett, who was appointed by President Donald Trump, said in an earlier statement to POLITICO on Monday that there had been “no basis” for him to recuse himself in part because Citi wasn’t a named party in the case. He also noted that a disclosure form filed at the appeals court initially did not list credit card issuers as entities with a financial interest in the case.

“I am painstaking about my recusal obligations,” Willett added in the Tuesday statement, adding that his court’s “conflicts database screens every known variation of Citigroup” and that he sought recusal guidance from the court’s ethics adviser in the case.

Citi is a member of the U.S. Chamber of Commerce, Consumer Bankers Association and the American Bankers Association, which filed the lawsuit along with other groups. They argue that the CFPB exceeded its statutory authority and that the fee limits are illegal.

Several progressive watchdog groups on Tuesday called for Willett’s recusal.

“Judge Willett’s stock holdings in Chamber member Citigroup – a gigantic credit card company – pose an obvious conflict of interest,” said Jeff Hauser, executive director of the Revolving Door Project. “His decision to hear this case and affirm the Chamber’s egregious judge-shopping gambit makes a mockery of the notion of an independent judiciary.”

Tony Carrk, executive director of Accountable.US, said that Willett’s “financial conflicts of interest in this case are clear” and that he should recuse himself.

Venue fight continues: Willett was part of a panel of judges that issued a 2-1 decision Friday in favor of the industry in a contentious preliminary dispute over whether the case should be heard.

Willett’s opinion reversed a lower court ruling by Northern District of Texas Judge Mark Pittman, who had sided with the CFPB in concluding that the lawsuit did not belong in his Fort Worth courthouse and transferred the case to the District of Columbia.

Pittman, also a Trump appointee, carried out the appeals court’s order Monday, issuing an order dissolving his earlier transfer of the case to D.C. and reopening it in Fort Worth.

But it remains an open question of whether the D.C. court, which had already docketed the case and assigned it to Judge Amy Berman Jackson, an Obama appointee, plans to comply with the ruling from the 5th Circuit, which oversees only the federal courts in Texas, Louisiana and Mississippi.