"I don't know what national security risk there is," Akbar told HuffPost over the phone. "Maybe the CIA is scared I will go speak with congressmen and tell them more about who our drone victims are."

Akbar is the director of the Foundation for Fundamental Rights, a legal group that represents drone victims and is pursuing lawsuits to force the Pakistani government to stop the strikes. Without his assistance, he does not believe his clients, who are from tribal regions of Pakistan, will be willing to visit the U.S.

"It's a great opportunity but they are scared. There's a huge trust deficit. They don't trust the U.S.," he said.

Akbar said that since he started representing these victims of drone strikes, he has been forced to endure visa processing times of 14 months to enter the country.

"I don't have any issue getting a visa anywhere [else] within a few working days, it's only within the United States," he said. "It's only the drone work which has stopped my visas."

The State Department did not respond to a request for comment.

Rehman and his children have been granted visas to travel to the U.S., and in a statement Grayson called on officials to approve Akbar's visa as well.

"Without Mr. Akbar, Rafiq and his children will not be able to travel to the U.S.," Grayson said. "I encourage the State Department to approve Mr. Akbar’s visa immediately, so that Rafiq and his family can share their stories with Congress and the American public.”

Director Robert Greenwald's Brave New Foundation has started an online petition to the State Department to allow Akbar to travel to the United States.