WASHINGTON -- President Barack Obama hinted at possible plans to close the Guantanamo Bay prison through executive action as he signed an updated national defense authorization bill on Wednesday.

This is the sixth consecutive year that lawmakers have inserted language into the National Defense Authorization Act, or NDAA, that outlaws the transfer of Guantanamo prisoners to U.S. soil. Because there are some prisoners at Guantanamo Bay who cannot be charged with a crime but are deemed too dangerous to release, the restriction on transferring prisoners to the U.S. effectively blocks Obama from fulfilling his campaign promise to close the notorious prison.

Obama vetoed a previous version of this years NDAA in October, citing his opposition to the Guantanamo restrictions and a continued reliance on a wartime slush fund that enabled Congress to avoid making meaningful cuts to the defense budget. Lawmakers subsequently rectified the spending issue, but left the Guantanamo provisions in place -- largely because they did not believe the president would veto the new bill based solely on the Guantanamo restrictions.

They were correct.

But when Obama signed the final defense authorization of his administration into law on Wednesday, he indicated that he did not feel entirely bound by Guantanamo-related restrictions.

Under certain circumstances, the provisions in this bill concerning detainee transfers would violate constitutional separation of powers principles, he wrote in a lengthy signing statement focused largely on his opposition to the unwarranted and counterproductive Guantanamo clauses.

Former Obama administration lawyers have made this point in the past, arguing that according to the Constitution, it is the commander-in-chiefs prerogative to dictate where to hold prisoners detained under the laws of war.

The president warned lawmakers, In the event that the restrictions on the transfer of detainees operate in a manner that violates these constitutional principles, my Administration will implement them in a manner that avoids the constitutional conflict.

In other words, Obama may claim constitutional authority to override Congress on future detainee transfers.

There are currently 107 detainees at Guantanamo Bay, including 48 who are cleared for release and seven who face charges in the militarys war court.

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