Mrs. Kirchner has said negotiating with Iran was the only way to move forward with an investigation that had been paralyzed for years.
After Mr. Nisman was found dead on Jan. 18, 2015, the bombing case stalled in the courts until a judge in 2017 indicted Mrs. Kirchner and other officials in her former administration. (Mr. Nisman’s death remains unsolved.)
In its ruling on Thursday, the three-judge panel said that the case should not go to trial because the agreement with Iran, regardless of its merits, “did not constitute a crime.”
The decision infuriated families of the victims and Jewish groups in Argentina.
“We’ve been waiting for three years for them to set a date for the trial, and now they decide that it isn’t a crime?” Tomás Farini Duggan, a lawyer representing family members of the victims, said in a local radio interview.
Mr. Duggan predicted the case would eventually reach the Supreme Court. Jewish leaders said they looked forward to having a day in court.
“Of course we don’t agree with this decision; in order to determine whether there was a crime or not, there must be a trial first,” said Jorge Knoblovits, the head of the Delegación de Asociaciones Israelitas Argentinas, which represents more than 100 Jewish organizations in Argentina.