Nearly all of these ex-convicts, however, lie low and steer clear of militancy, often under the watchful eye of family, mosque and community, lawyers and advocates say. A dozen former inmates declined to be interviewed, saying that to be associated publicly with a terrorism case could derail new jobs and lives. As for Mr. Royer, he is approaching only the midpoint of his 20-year sentence.

Did he get what he deserved? Chris Heffelfinger, a terrorism analyst and author of “Radical Islam in America,” did a detailed study of the Virginia jihad case, and concluded that Mr. Royer’s sentence was perhaps double what his crime merited. But he said the prosecution was warranted and probably prevented at least some of the men Mr. Royer assisted from joining the Taliban.

“I think a strong law enforcement response to cases like this is appropriate nine times out of 10,” Mr. Heffelfinger said. Mr. Royer himself, in his long presentencing letter to Judge Leonie M. Brinkema, said he understood why he had been arrested. “I realize that the government has a legitimate interest in protecting the public from terrorism,” he wrote, “and that in this post-9/11 environment, it must take all reasonable precautions.”

Today, Mr. Royer’s only battle is to serve out his sentence in a less restrictive prison nearer his children. In what he called in a letter “a heroic sacrifice,” his parents, Ray and Nancy Royer, moved from Missouri to Virginia to be close to their son’s children, now aged 8 to 12.

“I found it necessary to be a surrogate father,” said Ray Royer, 70, a commercial photographer by trade, in an interview at the retirement community outside Washington where he and his wife now live. When his son, who still goes by Randy in the family, converted to Islam at the age of 18, his parents did not object. Later, when he headed to Bosnia, they chalked it up to his active social conscience. “Religion is a personal thing,” the elder Mr. Royer said. “He’d never been in trouble.”

Ray Royer was at his son’s Virginia apartment in 2003 when the F.B.I. knocked at 5 a.m., put him in handcuffs and took him away. Now, years later, he alternates between defending his son and expressing dismay at what Randy got himself into.

“He did help his buddies get to L.E.T.,” or Lashkar-e-Taiba, the Pakistani militant group later designated as a terrorist organization. “He admitted to it. He should pay the price.” Still, he added, “maybe he deserved five years or so. Not 20.”