Massoud Shafii, who acted as defence attorney for three Americans detained in Iran, was briefly arrested and interrogated about the recent media appearances of his former clients.
Shafii told the International Campaign for Human Rights in Iran that he was arrested for a few hours on Tuesday morning while his home and office were searched.
He reported that officials appeared at his home with a warrant. In the end, he said, all the confiscated documents and computers were returned to him.
He indicated that all questioning related to the two recently released Americans, Shane Bauer and Josh Fattal.
Shafii said he told authorities that he should not be held responsible for the subsequent activities of Fattal and Bauer, adding that he believed the two were innocent and he had defended them accordingly, as was the duty of their defence attorney.
Bauer and Fattal were sentenced to eight years in prison for illegal entry and spying. They were finally released last Wednesday on bail and left for the US. Soon after they appeared at a press conference in New York, claiming their innocence and criticizing the Iranian government for mistreating political prisoners.
Shafii expressed concern that he may be banned from travelling abroad.
Fattal and Bauer were arrested together with their companion Sarah Shourd in the summer of 2009 near the Iran-Iraq border for illegal entry into Iran.
Shourd had been released on bail a year ago on medical grounds.