President Trump, who is facing multiple civil cases in New York and potentially criminal cases elsewhere, had his lawsuit against the New York Times, in which he claimed there was an “insidious plot” against him, thrown out of court Wednesday.

A New York state supreme court judge of Dutchess County, Robert Reed, tossed the former president’s lawsuit, writing that the newsgathering conducted by the Times was “at the very core of protected First Amendment activity.”

Mr. Trump’s lawsuit was against Times and three of its reporters for its Pulitzer Prize-winning 2018 coverage of Mr. Trump’s tax returns and how he came into his wealth.

In the lawsuit, Mr. Trump claimed that the reporters had hatched an “insidious plot” in concert with a psychologist and relative of the president, Mary Trump, who tried to “smuggle records out of her attorney’s office and turn them over to the Times.”

Judge Reed also ordered Mr. Trump to pay the legal fees of the Times as well as its reporters, Susanne Craig, David Barstow, and Russ Buettner.

According to Mr. Trump, the reporting violated a confidentiality agreement that Ms. Trump signed in 2001, when the two were settling a battle over the will of Mr. Trump’s father, Frederick Trump.

Judge Reed, though, did not see merit in Mr. Trump’s suit, writing that his “claims against The Times defendants, as an initial matter, fail as a matter of constitutional law.”

Mr. Trump’s lawyer, Alina Habba, has not yet said if the legal team plans to appeal the ruling, but said in a statement to the Times that “we will weigh our client’s options and continue to vigorously fight on his behalf.

“All journalists must be held accountable when they commit civil wrongs,” Ms. Habba said, maintaining that reporters “went well beyond the conventional news-gathering techniques permitted by the First Amendment.”

A spokesman for the Times, Charlie Stadtlander, said that the paper is “pleased with the judge’s decision today.

“It is an important precedent reaffirming that the press is protected when it engages in routine news gathering to obtain information of vital importance to the public,” Mr. Stadtlander said.

Although Mr. Trump’s case against the Times was thrown out, he has multiple legal cases pending in the Empire State, including a civil case concerning the alleged rape of writer E. Jean Carroll and a criminal case in which Mr. Trump faces 34 felony counts alleging he falsified business records related to hush money payments to adult film actress Stephanie Gregory Clifford, better known as Stormy Daniels.