Justice Samuel A. Alito Jr. took the unusual step late Tuesday of responding to questions about his travel with a billionaire who frequently has cases before the Supreme Court hours before an article detailing their ties had even been published.

In an extraordinary salvo in a favored forum, Justice Alito defended himself in a pre-emptive article in the opinion pages of The Wall Street Journal before the news organization ProPublica posted its account of a luxury fishing trip in 2008.

His response comes as the justices face mounting scrutiny over their ethical obligations to report gifts and to recuse themselves from cases involving their benefactors. The latest revelations are sure to intensify calls for the court to adopt more stringent ethics rules.

The justices have taken differing approaches to explaining their actions and attempting to protect their institution. Justice Clarence Thomas has been largely silent in the face of revelations of gifts from Harlan Crow, a wealthy Republican donor. Chief Justice John G. Roberts Jr. turned down an invitation from Congress to testify about the court’s ethics practices and made vague statements about addressing them.

And Justice Alito has come out swinging.

The ProPublica article centered on a trip Justice Alito took to a remote part of Alaska, arriving on the private jet of Paul Singer, an immensely wealthy hedge fund manager and Republican donor. The flight would have cost more than $100,000 one way if the justice had chartered it himself, the outlet estimated, and his annual disclosures make no mention of the trip, in what many experts in legal ethics said was a violation of federal law. In the years afterward, Mr. Singer’s businesses were parties to a number of Supreme Court cases in which Justice Alito participated.

ProPublica had sought comment from the justice, who instead turned to The Journal to make two main points: that he was not required to recuse himself from those cases or to disclose the travel.

Justice Alito said he had spoken to Mr. Singer only a handful of times, including on two occasions when Mr. Singer introduced the justice before speeches. “It was and is my judgment that these facts would not cause a reasonable and unbiased person to doubt my ability to decide the matters in question impartially,” Justice Alito wrote.

He added that he did not know of Mr. Singer’s connection to the cases before the court, including one in which the court issued a 7-to-1 decision in favor of one of Mr. Singer’s businesses, with Justice Alito in the majority.

But Mr. Singer’s connection to the case, Republic of Argentina v. NML Capital, was widely reported. A Forbes article covering the decision bore the headline “Supreme Court Hands Billionaire Paul Singer a Victory Over Argentina.” An article in The New York Times noted that the parties to the case included “NML Capital, an affiliate of Elliott Management, the hedge fund founded by Paul Singer.”

Justice Alito said he was not required to disclose the trip on Mr. Singer’s private jet in “a seat that, as far as I am aware, would have otherwise been vacant.”

A federal law requires disclosures of gifts over a certain value but makes exceptions for “personal hospitality of any individual” at “the personal residence of that individual or his family or on property or facilities owned by that individual or his family.” Justice Alito wrote that a jet is such a facility, quoting from dictionary definitions.

In March, the Judicial Conference of the United States, the policymaking body for the federal courts, issued new guidelines requiring disclosure of travel by private jet and stays in commercial properties like resorts.

After ProPublica disclosed that Justice Thomas had taken a series of lavish vacations paid for by Mr. Crow, including extended stays on Mr. Crow’s yacht, the justice said he would comply with the revised rules. Justice Thomas justified accepting the trips because of what he said was his close friendship with Mr. Crow.

In his essay, Justice Alito disputed the notion that the fishing trip was particularly fancy and ProPublica’s account of extravagant meals topped with expensive bottles of wine. “I stayed for three nights in a modest one-room unit at the King Salmon Lodge, which was a comfortable but rustic facility,” he wrote. “As I recall, the meals were home-style fare. I cannot recall whether the group at the lodge, about 20 people, was served wine, but if there was wine it was certainly not wine that costs $1,000.”

Among those who helped organize the trip, according to ProPublica, was Leonard Leo, a longtime leader of the Federalist Society, the conservative legal group, who was also in attendance. In a statement to ProPublica, Mr. Leo wrote that justices across the ideological spectrum had received hospitality from friends and supporters and that their judicial work had been unaffected.

“We all should wonder whether this recent rash of ProPublica stories questioning the integrity of only conservative Supreme Court justices is bait for reeling in more dark money from woke billionaires who want to damage this Supreme Court and remake it into one that will disregard the law by rubber stamping their disordered and highly unpopular cultural preferences,” Mr. Leo said.

Justice Alito appears to have a good relationship with The Journal’s opinion pages, which published a wide-ranging interview with him in April.

He said at the time that he was disappointed that lawyers had not come to the defense of the court, which was facing mounting scrutiny for what critics say are serious ethical lapses.

“This type of concerted attack on the court and on individual justices” is, he said, “new during my lifetime.”

He added: “The idea has always been that judges are not supposed to respond to criticisms, but if the courts are being unfairly attacked, the organized bar will come to their defense.”

Instead, Justice Alito said, “if anything, they’ve participated to some degree in these attacks.”

A few days before Politico published a leaked draft of Justice Alito’s majority opinion overturning Roe v. Wade last year, an editorial in The Journal provided hints about tensions at the court that appeared to be based on inside knowledge.

The author of the majority opinion was not yet publicly known. “Our guess,” the editorial said, correctly, was that it would be Justice Alito.

Recent revelations have brought into sharp focus how few disclosure requirements are in place and how the justices are often left to police themselves.

Gabe Roth, executive director of Fix the Court, an advocacy group that seeks more openness at the Supreme Court, said it was in need of an ethics overhaul. “The public should expect Supreme Court justices of all people to be ethical exemplars,” he said, “yet the nine have consistently been shown to be deficient in this regard.”

Last month, the chief justice said the court aimed to address the matter even as he suggested that Congress was unable to act under the Constitution’s separation of powers.

“I want to assure people that I am committed to making certain that we as a court adhere to the highest standards of conduct,” he said. “We are continuing to look at things we can do to give practical effect to that commitment.”