ProPublica released a report on Friday revealing details about US Supreme Court Justice Clarence Thomas’ attendance at the Koch network annual winter donor summit in California in 2018. According to the report, Thomas attended a private dinner at the event and did not report his flight to California on his annual financial report, echoing similar reporting from earlier this year.

The report states that Thomas attended the event usually attended by donors to the Koch network, who “typically have to give at least $100,000 a year. Those who give in the millions receive special treatment, including dinners with Charles Koch and high-profile guests.” According to the report, Thomas arrived at the event in a private jet, which was not reported on his annual financial report. However, the report says that a Koch spokesperson said the network did not pay for the flight.

Under federal law, federal judges are required to report specific financial gifts. Additionally, there can be civil sanctions and criminal penalties for knowingly and willingly falsifying a report or failing to file a report. Also, Canon 4 of the Code of Conduct for US Judges advises federal judges not to participate in “extrajudicial activities that detract from the dignity of the judge’s office, interfere with the performance of the judge’s official duties, reflect adversely on the judge’s impartiality, lead to frequent disqualification, or violate the limitations set forth below.” However, the code is not mandatory for US Supreme Court justices. That said, it is customary for them to adhere to it in practice.

Libertarian billionaires Charles and David Koch founded the Koch network together. The report notes that the network is “an overlapping set of nonprofits” that have lobbied for libertarian policies. Libertarians generally believe “that most (if not all) of the claims to special authority made by the various governments around the world are unjustifiable.”

This is not the first controversy surrounding Thomas. In August, ProPublica released another report revealing details about Thomas’ history of accepting lavish gifts while serving as a US Supreme Court justice. In response to these controversies, Congress has advanced a bill that proposes ethics reforms for the US Supreme Court.