But Armed Services committees in the House and Senate in December agreed on a plan that made it easier to draw down the prison population. Both Montana Sens. Tester and Max Baucus supported that plan.

“What they did in December was, Congress passed a new law that makes it easier to pass detainees back to foreign countries,” said Chris Anders, senior legislative counsel in the American Civil Liberties Union’s Washington, D.C., office.

The ACLU has for years argued against the detention of Guantanamo prisoners. There are 77 detainees who have been cleared for release but remain imprisoned. Another 45 detainees are considered by the federal government to be too dangerous to release, but government also says it doesn’t have enough evidence to prosecute the men.

The 155 are what remains of the 779 held at the facility since it opened in 2002.

President George W. Bush released 532 prisoners during his tenure. Obama has released 89. Roughly 92 percent of the detainees were not classified as al-Qaida fighters.

Anders said the ACLU is lobbying for the release of the detainees already cleared to go and trials for the detainees that have not been cleared.

During the Havana part of the delegation visit, Tester and the others met with Gross.