A federal judge has thrown out former Trump campaign volunteer Carter Page’s defamation, terrorism and fraud lawsuit against a media giant whose news story was rooted in the infamous Christopher Steele dossier.

Six other dossier-related libel suits in London, New York, Washington and Florida remain.

On Sept. 23, 2016, bestselling author Michael Isikoff of Yahoo News wrote what has come to be one of the more infamous news stories in the saga of the dossier, the Russians and the Donald Trump campaign.

Mr. Isikoff had just met secretly in a Washington hotel room with Mr. Steele, flown in from London at the behest of investigative firm Fusion GPS. Its co-founder, Glenn Simpson, hired Mr. Steele, a British ex-spy, to uncover Russian dirt on candidate Trump with money from the Democratic National Committee and the Hillary Clinton campaign.

Mr. Isikoff’s story relayed one of Mr. Steele’s major felony charges, though quoting a “Western intelligence source,” not Mr. Steele and his opposition research: Mr. Page, while in Moscow to deliver a public speech at a university in July 2016, met with two powerful Kremlin figures, Igor Sechin and Igor Diveykin. Mr. Steele’s dossier said Mr. Page was offered bribes for advocating economic sanctions relief.

Mr. Page, a pro-Russia energy investor who once lived in Moscow, has steadfastly denied under oath that such meetings ever occurred or that he has ever met the two men.

A year after the story appeared, Mr. Page, acting as his own lawyer, filed the lawsuit in U.S. District Court in New York against Yahoo News owner Oath Inc., part of the Verizon conglomerate.

U.S. District Judge Lorna G. Schofield dismissed the suit March 20, but never fully addressed the libel argument in her decision.

Instead, Judge Schofield, who was appointed by President Barack Obama in 2012, first discussed Mr. Page’s federal complaints — that the article violated the U.S. Anti-Terrorism Act and was fraudulent.

“The Complaint lacks sufficient factual allegations to state a claim under the ATA,” she wrote.

With the federal complaints out of the way, the judge said the defamation charge was moot because it is a state law claim. “A [U.S.] district court may decline to exercise supplemental jurisdiction” if the federal claims have been dismissed, she wrote.

Mr. Isikoff has defended his article, saying its main thrust was that the FBI had opened an investigation into possible Russian interference in the 2016 election, which it had.

In a filing, Oath Inc.’s lawyers said: “The September 23 Article reported that U.S. officials received intelligence reports that Dr. Page had met with Sechin and Diveykin — two individuals currently under U.S. sanctions — while in Moscow. This is substantially true. The September 23 Article did not say or imply that these meetings actually occurred; it reported only that U.S. Officials had received intelligence reports about Dr. Page’s alleged meetings.”

Judge Schofield accepted that interpretation in throwing out Mr. Page’s fraud charge.

“The Article does not say that Plaintiff actually met with the two Russians, but rather that U.S. officials had received reports of such meetings,” she said. “The substance and even headline of the Article express uncertainty about the occurrence and substance of any such meetings. That some readers may have assumed that the meetings occurred does not constitute fraud by the Article’s publisher.”

Mr. Page argues that the Yahoo report was not based on “intelligence” but on Democratic Party opposition research that had been recirculated until it ended up with the FBI and politicians.

“These and other false statements throughout the 2016 Yahoo report carry the deceitful implication that the documents referred to were actual U.S. Government reports rather than opposition political research by Christopher Steele, a consultant hired by associates and/or supporters of the Clinton Campaign,” he said.

Mr. Page told The Washington Times he plans to amend his complaint. Judge Schofield said Mr. Page erred in naming Oath Inc. as the defendant because he didn’t present facts that show the parent company was involved in writing the story.

“Once again in New York and as previously seen in Washington, powerful parties have managed to initially steer a district court judge away from the truth regarding illegal interference in the U.S. election and the associated civil rights abuses that helped to make it all possible,” Mr. Page said.

‘Russian Roulette’

Mr. Page is at the center of Republican charges that the FBI abused the process for obtaining a court-ordered wiretaps via the Foreign Surveillance Intelligence Act (FISA).

An investigation spearheaded by Rep. Devin Nunes, California Republican and chairman of the House Permanent Select Committee on Intelligence, discovered that the FBI used Mr. Steele’s opposition research to persuade a judge to order a year’s worth of wiretaps on Mr. Page, beginning Oct. 21, 2016.

The committee’s Republican majority last week ended its Russia-Trump probe and issued a brief report saying the panel found no evidence of Trump-Moscow collusion. Democrats did not agree and want the investigation to go on.

Mr. Page has not been charged. The dossier makes at least 10 allegations of Russia-Trump election collusion. None has been confirmed publicly by special counsel Robert Mueller or congressional investigations.

President Trump reasserted Sunday via Twitter that there was no collusion during the campaign.

Mr. Mueller and his staff of nearly 20 prosecutors and scores of FBI agents will have the final say and have given no indication they are nearing completion.

With the Page libel lawsuit dismissed, there remain six defamation court cases stemming directly from the dossier.

In London last week, a court master ruled that Mr. Steele must undergo questioning from lawyers for Aleksej Gubarev, a Russian technology entrepreneur with operations in Florida.

Mr. Gubarev filed libel lawsuits against Mr. Steele in London. He also sued BuzzFeed, a news website that posted the unverified dossier on Jan. 10, 2017, in U.S. District Court in Florida. That trial is scheduled to begin in August.

Mr. Steele’s December 2016 dossier memo, its last, accused Mr. Gubarev of directly taking part in the hacking of Democratic Party computers. The entrepreneur denies the charge, and his lawyers say there is absolutely no evidence their client was involved in any hacking.

BuzzFeed redacted Mr. Gubarev’s name and apologized. It has hired a consulting firm, including a former FBI cybersecurity expert, to try to prove that the dossier is true.

Mr. Steele has acknowledged in a London court filing that the Gubarev tips were unsolicited and unverified.

Meanwhile, Mr. Isikoff teamed up with David Corn, a writer for left-leaning Mother Jones magazine, to write a book about Mr. Trump’s and his associates’ ties to Russians. “Russian Roulette” debuted at No. 1 on the New York Times bestseller, non-fiction list on Sunday.

“Dishonesty sells,” Mr. Page said.

Mr. Trump has been in the land development business for four decades. He looked at deals in Russia several times, but has never built or franchised a hotel or apartment building there.

“Russian Roulette” is the second anti-Trump book to achieve that No. 1 status, following Michael Wolff’s “Fire and Fury.” The new book paints a sympathetic portrait of Mr. Steele, who has become a hero to some Democrats in Congress and to liberals in general. The book says the dossier’s information on Mr. Page’s supposed Kremlin meetings came from the lover of a Kremlin figure.

Mr. Steele paid a subcontractor to collect information from unnamed Kremlin figures, whose narrations he put into 17 memos from June 2016 to December 2016.

Fusion and Mr. Steele tried to sell the allegations to reporters during the election. The only ones to publish the information before Nov. 8 were Mr. Isikoff and Mr. Corn.

Mr. Steele told a contact at the Justice Department that he was “desperate” to sink the Trump campaign. He also has alleged an “extensive conspiracy” between the Trump campaign and the Kremlin that has yet to be confirmed publicly.

“It’s hard to conceive of a more villainous, personal, large-scale attack based on complete lies and propaganda,” Mr. Page told The Times.