Ms. Hughes said one of her former clients had been denied asylum because he paid a ransom to an armed group in order to release a kidnapped family member. “It’s a fairly widespread problem that’s not limited to Syrians,” she said.

Eric Schwartz, a former Obama administration official and now the president of Refugees International, called the provision in immigration law “a product of the post 9/11 environment” — one that government officials had subsequently recognized was so broad that it caught all kinds of people in its net. “You had legislation that broadly expanded the definition of terrorist activity, captured people who could have been coerced into terrorist activity and created this Tier III catchall category,” he said.

Mary A. Cabrera, a spokeswoman for Citizenship and Immigration Services, said the agency did not keep a set list of undesignated terrorist organizations, but made case-by-case determinations. Ms. Cabrera said she could not comment on an individual case.

Mr. Ziadeh chronicled his experience in an affidavit as part of his original asylum application. He said in the affidavit that he had been repeatedly called in for interrogation by the secret police in Syria. He edited a political magazine that was shut down by the government, founded the Damascus Center for Human Rights Studies and visited the United States in 2006 at the invitation of the State Department’s international visitor program.

He returned to Syria only to be summoned for interrogation by the authorities and then banned from traveling abroad. In 2007, on the pretext of getting medicine for his sick father, he obtained permission to go to neighboring Jordan for a day and secretly procured a visa from the American Embassy in Damascus. As soon as he reached Jordan, he and his wife boarded a flight to the United States.

The next year, the Syrian government issued a warrant for his arrest and barred his mother and siblings from leaving the country. When the Syrian uprising began in 2011, he received a frightening email telling him to be “careful” about his mother, still in Syria.

Later that year, his brother, who was not politically active, was arrested; Mr. Ziadeh believes it was payback for his activism. His cousin was killed in what he called a massacre in the family’s hometown, Daraya. His mother and siblings slipped out of the country as soon as they could. They are scattered across Jordan, Turkey and Saudi Arabia.