This spring, one of the students, Mr. Hart, submitted a clemency petition for Corey Clagett, a former Army private who pleaded guilty to shooting two unarmed detainees in Iraq in 2006 — killings that an Army investigation found were ordered by Mr. Clagett’s staff sergeant. The staff sergeant, Raymond Girouard, was also convicted in the killings, but his case was dismissed on appeal. He was given back pay and discharged under honorable conditions after serving three and a half years in prison. Mr. Clagett was sentenced to 18 years.

As part of the project, United American Patriots paid for Mr. Hart and other students to fly to Fort Leavenworth, Kan., to interview the prisoners. “Before that, I didn’t understand how confusing things were on the ground in Iraq, how arbitrary the brutality was,” Mr. Hart said.

The students and United American Patriots approach the issue differently. United American Patriots says troops sometimes are held to unfair standards by senior officers who know little about combat.

“In Vietnam I was supposed to radio in to ask permission every time I opened fire, but there wasn’t time,” Mr. Donahue said. “So after my second patrol, I never called back to request permission until I was sitting on a mountain of bodies. Today, you couldn’t do that. It’s gotten so a guy has to have a lawyer in the foxhole next to him. If I had it the way guys do today, I’d have been court-martialed a thousand times.”

The law school group, led by Mark Heyrman of the school’s legal aid clinic, is reluctant to embrace that argument and is looking instead toward issues like mental health. “We agree on the bottom line, that soldiers are being excessively punished,” Mr. Heyrman said. “The concern is that United American Patriots are trying to say we should go back to the way we did it in Vietnam. I don’t know if that is a winning public message.” Mr. Heyrman, who worked with Mr. Obama when he was a law professor at the University of Chicago, said he doubted that argument would work with the president.

For both groups mercy has its limits. They chose not to be advocates of troops convicted of premeditated crimes that combined rape and murder. But after some debate they decided to urge leniency for Mr. Bales despite his guilty plea to 16 killings in a small village.