An Egyptian court dropped all remaining criminal charges against former President Hosni Mubarak on Saturday in a sweeping repudiation of the Arab Spring uprising that forced him from power.

The court dismissed murder charges against Mr. Mubarak in the killing of protesters demanding an end to his 30-year rule — charges that once inspired crowds to hang the president’s effigy from the lampposts of Tahrir Square in Cairo and captivated the region. His reviled security chief and a half-dozen top police officials were acquitted.

The court also acquitted Mr. Mubarak, his two sons and a wealthy business associate of corruption charges; the three others had come to personify the rampant self-dealing of Mr. Mubarak’s era as much as the president himself.

If normal legal procedures are followed, Mr. Mubarak could soon go free for the first time since his top generals removed him from power amid a popular revolt in 2011, although it was not clear whether those rules would be adhered to.

About 1,000 demonstrators gathered around Tahrir Square at night to protest the decision, but heavily armed security forces had closed off the symbolic roundabout and by 9 p.m. the police were firing tear gas and birdshot to drive away the crowds.

More than five months after the inauguration of a military-backed strongman, President Abdel-Fattah el-Sisi, the authorities appeared to calculate that the Egyptian public was so weary of unrest that it had lost a desire for retribution against Mr. Mubarak, or at least that they now had a firm enough grip to suppress any backlash.

“Today’s verdict indicates a very deliberate decision by the regime to continue on the path of rewriting the history that led to Mubarak’s ouster and closing the file on the Jan. 25 revolution,” said Hossam Bahgat, a journalist and human rights advocate who had cheered on that revolt and is now studying in New York.

The council of generals who took power from Mr. Mubarak had feared a public backlash too much to ever allow the former president’s release, but Mr. Sisi’s government felt no such compunction, Mr. Bahgat said. “They are not afraid,” he said. “They are perfectly capable of letting him walk free, and they feel no pressure to hold him accountable.”

Mr. Mubarak, 86, who has been held at a military hospital because of frail health, appeared in court on a stretcher in sunglasses, a blue necktie and sweater. He remained stone-faced as the chief judge, Mahmoud Kamel al-Rashidi, read the verdict. Only at the end did he allow himself a smile as his two sons, Alaa and Gamal, hugged and kissed him.

A short time later, Mr. Mubarak was photographed waving to admirers from a hospital balcony. In a telephone interview with a supportive, pro-government talk show host, the former president scoffed at an earlier guilty verdict against him. “I laughed when I heard the first verdict,” he said. He suggested a conspiracy had been behind the 2011 uprising.

“They turned on us,” he said, and when asked if he meant “the Americans,” he replied that he could not explain over the phone. “I can’t tell you if it’s the Americans or who.”

Judge Rashidi, who led a panel of three judges, did not elaborate from the bench on their reasoning, pointing instead to a 280-page summary of their 1,340-page explanation of the case.

He insisted that the ruling had “nothing to do with politics.” He acknowledged the “feebleness” and corruption of Mr. Mubarak’s later years in power, and he lauded the rallying cry of the 2011 revolution — bread, freedom and social justice.

But at other times he sounded sympathetic to the former president. “To rule for or against him after he has become old will be left to history and the Judge of Judges,” he said.

Judge Rashidi did not explain from the bench why he had dismissed the murder charges. Legal analysts said the judge had faulted the way Mr. Mubarak had been added to an existing case. He acquitted Mr. Mubarak and his friend, the businessman Hussein Salem, of corruption charges involving allegations that they had conspired to sell Egyptian natural gas to Israel at below-market prices. And he acquitted Mr. Mubarak and his sons of charges that Mr. Salem gave them vacation homes on the Red Sea as kickbacks in a land deal. (Mr. Salem fled to Spain in 2011 and was tried in absentia.)

In May, Mr. Mubarak was sentenced to three years in prison in a separate corruption case involving lavish, government-funded improvements to his and his sons’ personal homes. But he has now spent more than three years in custody on various charges, and under Egyptian law he has thus served the requisite time and could be released.

The prosecutor has the right to appeal, but it was not immediately clear if he planned to do so.

The first sessions of Mr. Mubarak’s trial were often rowdy and loud, with a courtroom full of human rights lawyers demanding retribution for the demonstrators who had been killed and for decades of brutal autocracy.

But the changed context was evident from the start. Judge Rashidi warned that anyone who interrupted his reading of the decision would be sentenced to a year in jail, and the spectators stayed obediently quiet.

And the courtroom was packed with Mubarak supporters instead of human rights lawyers. As soon as the judge finished, the room erupted in jubilation.

Commentators in the state-run and pro-government news media suggested that it was time to move on from the 2011 revolution and its aftermath. “We have to turn this page, and the long state of argument that has lasted for years,” Dalia Ziada, director of the Liberal Democracy Institute and a supporter of Mr. Sisi, said in an interview.