Trump administration officials argue that it is more productive to voice their criticisms of Mr. Sisi in private. They have pointed as vindication of their policy to the release of Ms. Hijazi, an American aid worker detained for three years in Egypt. She was free weeks after Mr. Sisi visited the White House in April. But at least 20 other Americans, including Mr. Etiwy, are still held in Egyptian jails.

In Dublin, Mr. Halawa’s sisters ululated and hugged one another outside their home in a suburban housing development. Speaking by phone, his sister Nosayba said family members had fallen to their knees in relief when they heard the verdict. “Then we went back to crying and hugging each other,” she said.

Image Mr. Halawa celebrated moments after his acquittal on charges related to a 2013 political protest. Credit... Declan Walsh/The New York Times

In New York, Mr. Etiwy’s family was “heartbroken,” said his American lawyer, Praveen Madhiraju. Mr. Madhiraju said he had asked the State Department to pressure the Egyptian government to release his client, citing a United States statute that obliges the president to demand the release of Americans unlawfully imprisoned abroad.

“Aside the law, it’s just morally the president’s obligation,” Mr. Madhiraju said.

The mass trial stemmed from one of the bloodiest, most politically charged moments in recent Egyptian history. On Aug. 14, 2013, Egyptian security forces killed at least 800 people in central Cairo as they dispersed Muslim Brotherhood supporters who had gathered to protest the ouster of Mohamed Morsi, the country’s elected president, by the military a month earlier.

Days later a second protest, this time against the military, in Ramses Square in Cairo turned violent, with hundreds of people taking refuge in a mosque. After a protracted standoff, the police cleared the protesters from the mosque, arresting hundreds of people, including Mr. Halawa and three of his sisters.

Mr. Halawa’s sisters were released on bail and returned home to Ireland, but their brother faced charges that carried a potential death penalty. His case become a national cause in Ireland, leading to visits to Egypt by an Irish parliamentary delegation last January, and direct lobbying by successive Irish prime ministers.