Story highlights

It is not immediately clear why Lori Berenson was not allowed to leave Peru

Her lawyer characterizes the decision as "arbitrary"

A U.S. State Department official says some paperwork issues are being worked out

CNN  — 

Lori Berenson was prevented from leaving Peru although a court has given the American activist permission to travel to the United States for the holidays, her lawyer told CNN en Espanol on Saturday.

Berenson and her 2-1/2-year-old son were stopped at the airport for reasons that were not immediately clear, said Anibal Apari.

He characterized the decision to block their leaving as “arbitrary,” and said he wanted to get to the bottom of who gave the order.

Berenson was sentenced to life in prison in 1995 for collaborating with the Tupac Amaru Revolutionary Movement to attack the nation’s congress and overthrow the government. Her sentence was reduced to 20 years on appeal.

She was released from Lima’s Chorrillos Penitentiary in November 2010 after a Peruvian court granted her parole. As a parolee, Berenson must remain in Peru until at least 2015.

If she had been allowed to leave, it would have been the first time she left Peru in 16 years. Under the travel terms set by the Lima court, Berenson, 42, would have to return to Peru in early January.

“We understand there were some paperwork issues that are being worked through. We can’t comment further because of privacy considerations,” said a U.S. State Department official, who declined to speak on the record because of the sensitivity of the situation.

A call to Berenson’s parents in New York on Saturday was not immediately returned.

In 2009, while in prison, Berenson gave birth to a son who was fathered by Apari, her estranged husband who is also her attorney. The boy had been living with her in prison until her release.

Apari had previously told CNN that the court approved Berenson’s petition to travel, but did not specify a date saying they wanted to keep their plans private for their own protection.

CNN’s Jamie Crawford contributed to this report.