LONDON — A military court in the Jordanian capital, Amman, on Thursday acquitted a militant Islamic cleric known as Abu Qatada on charges of planning a terrorist attack on an American school there in the late 1990s, the latest chapter in a longstanding legal fight that included a death sentence in absentia, a 10-year court battle in Britain and his deportation a year ago.

The court said it had found insufficient evidence to convict the cleric. The verdict appeared to be a remarkable reversal of one in Jordan more than 14 years ago, in which he was convicted in absentia and sentenced to death, later commuted to life imprisonment with hard labor. Supporters of the cleric, who was once described by a Spanish judge as Osama bin Laden’s “right-hand man in Europe,” are certain to depict his acquittal as a vindication of his protestations of innocence.

“I think that justice has taken its place here today,” the cleric’s lawyer, Ghazi Thneibat, told reporters, according to The Associated Press.

“We are happy,” said Umm Ahmed, his sister. “But I want him to leave with us.”

The 54-year-old cleric, whose real name is Omar Mahmoud Mohammed Othman, will continue to be held in connection with a separate case relating to a plot to bomb Israeli, American and other Western tourists at millennium celebrations in 2000, news reports said. Mr. Othman has denied all the charges against him.