For years, conservative billionaires have treated Supreme Court justice Clarence Thomas to opulent vacations and trips on their private jets. If these were anything other than disinterested gifts, then they’re taxable — and Thomas owes the IRS a huge bill.

When Supreme Court justice Clarence Thomas flouted longstanding ethics laws by refusing to disclose billionaire gifts, he avoided public outrage for years. Based on new revelations about the potential motivations behind those gifts, he also may have avoided laws requiring Americans to pay taxes on such donations, legal experts say.

Recent reporting from ProPublica revealed that Thomas was showered with luxury gifts from wealthy benefactors, including vacations, private flights, school tuition, and even a loan for a high-end RV. Though Thomas has insisted the gifts were just the innocent generosity of friends, many came after he threatened to resign over the justices’ low salaries — and one of Thomas’s vacation companions said the money was given to supplement the justice’s “limited salary.”

According to experts, if these benefits were given to Thomas as a way to buttress his regular pay and keep him on the court, they could be considered a taxable transaction rather than a gift. By refusing to publicly disclose such transactions, Thomas made it impossible for watchdog groups to alert tax-enforcement officials about the potential issue in real time.