A billionaire conservative donor whose hedge fund would later have business before the Supreme Court flew Justice Samuel Alito on his private jet to a luxury fishing trip in Alaska in 2008, ProPublica reported late Tuesday night, the latest story raising questions about ethics standards on the high court.

Alito neither disclosed the travel nor recused himself from a 2014 case in which he voted in the 7-1 majority in favor of Paul Singer’s hedge fund. The fund, which was locked in a dispute with Argentina, was ultimately paid $2.4 billion, according to ProPublica. 

Singer’s hedge fund, Elliott Management, came before the Supreme Court at least 10 times following the trip, the report said.

ProPublica also reported that another wealthy businessman, whom it did not name, provided expensive vacations to Alito and Justice Antonin Scalia, who died in 2016. Alito stayed at a commercial fishing lodge owned by the businessman, a major conservative donor, during the Alaska trip, the news organization reported. Three years earlier, that businessman flew Scalia on a private jet to Alaska and paid the bill for his stay, according to ProPublica.

Leonard Leo, the longtime leader of the conservative Federalist Society, which has gained influence in the nomination of federal judges and Supreme Court justices, organized the 2008 trip Alito was on, the report said. Leo invited Singer to join and then asked Singer if he and Alito could fly on the billionaire's plane, a person familiar with the trip told ProPublica.

If Alito had chartered the flight himself, it could have cost more than $100,000 one way, and the fishing lodge charged more than $1,000 a day, according to the report.

ProPublica reported that Singer has contributed more than $80 million to Republican political groups and millions more to the Manhattan Institute, a conservative think tank that he chairs and which regularly files friend-of-the-court briefings with the Supreme Court.

Instead of directly answering questions emailed by ProPublica, Alito responded with an op-ed in The Wall Street Journal, titled “ProPublica Misleads Its Readers,” which was published before ProPublica’s report went live.

He insisted that neither accusation made against him — that he should have recused himself and that he was obligated to disclose the travel accommodations as gifts — was valid.

Alito said “recusal would not have been required or appropriate” because he has spoken to Singer “on no more than a handful of occasions.” The justice said, with the exception of the fishing trip, all of the exchanges have been brief and casual, adding that the men never discussed Singer’s business or any case or issue before the Supreme Court.

Alito also said he was unaware of Singer’s connection to any cases before the high court because Singer was not listed as a party on any filings. ProPublica reported that Singer’s role in the cases had been often covered by the legal press and mainstream media.

In addition, Alito said he was invited to fly on Singer’s plane shortly before the event and occupied a seat “that, as far as I am aware, would have otherwise been vacant. It was my understanding that this would not impose any extra cost on Mr. Singer.”

The justice added that until recently financial disclosure instructions told judges that personal hospitality did not need to be reported and that justices commonly interpreted that to include accommodations and transportation for social events.

“The flight to Alaska was the only occasion when I have accepted transportation for a purely social event, and in doing so I followed what I understood to be standard practice,” Alito wrote. 

Ethics law experts ProPublica spoke to said Alito appears to have violated a federal law requiring justices to disclose most gifts. 

“If you were good friends, what were you doing ruling on his case?” said Charles Geyh, an Indiana University law professor and an expert on recusals, told the news organization. “And if you weren’t good friends, what were you doing accepting this [flight]?”

In April, ProPublica reported that billionaire Harlan Crow paid for private flights and luxury vacations for more than 20 years  for Justice Clarence Thomas and bought real estate from him, none of which was disclosed by the justice.

In a subsequent report, ProPublica reported that Crow paid thousands of dollars in private school tuition for Thomas’ great nephew, whom the justice had raised since he was 6 years old. 

And The Washington Post reported Leo, who organized the 2008 Alito fishing trip, arranged for Thomas’ wife, Ginni, to be paid tens of thousands of dollars in consulting fees just before Leo’s nonprofit, the Judicial Education Project, filed a brief to the Supreme Court in a landmark voting rights case.

Thomas, Crow and Leo have all denied any wrongdoing.

The Supreme Court almost entirely polices itself on ethics matters.

The Democratic-led Senate Judiciary Committee held a hearing last month in which lawmakers debated the possibility of strengthening ethics rules for justices. Republicans argued doing so would violate the Constitution’s separation of powers provision, but legal experts who testified were divided.

In a Twitter thread on Wednesday, Illinois Sen. Dick Durbin, the panel's chairman, said that the committee will begin marking up Supreme Court ethics legislation when lawmakers return from the upcoming July 4th recess.

"The Supreme Court is in an ethical crisis of its own making due to the acceptance of lavish gifts from parties with business before the Court that several Justices have not disclosed," Durbin wrote on Twitter. "The reputation and credibility of the Court are at stake."

"Chief Justice Roberts could resolve this today, but he has not acted," he continued. "The highest court in the land should not have the lowest ethical standards. But for too long that has been the case with the United States Supreme Court. That needs to change."

The Illinois Democrat expressed hope that Roberts would take action to enact a code of ethics, but added: "if the Court won’t act, then Congress must."