4 Detainees Transferred From Guantanamo on the Last Full Day of Obama's Presidency

They're the final transfers of the Obama administration.

Earlier, President Obama released a report to Congress that outlined his administration's efforts to close the detention facility.

In an accompanying letter, Obama criticized Republicans for blocking that effort from becoming a reality.

"There is simply no justification beyond politics for the Congress' insistence on keeping the facility open," Obama wrote. "Members of Congress who obstruct efforts to close the facility, given the stakes involved for our security, have abdicated their responsibility to the American people."

Congress has passed legislation that prevented the spending of funds to transfer Guantanamo detainees to detention facilities on the U.S. mainland.

Another 26 detainees are eligible for Periodic Review Boards that determine if they continue to pose a terror threat to the U.S. However, it is often assumed that these detainees will neither be eligible for prosecution nor transfers.

The Obama administration report sent to Congress said the annual cost of maintaining the camp is approximately $445 million. It estimated that maintaining the facility open would require an additional $225 million in construction and furnishing costs.