Congress has once again overwhelmingly passed a spending bill that seeks to block President Barack Obama from closing the military prison at Guantanamo Bay, and once again, Mr. Obama, after a bit of pouting, looks likely to sign it. That members of Congress have an irrational and destructive not-in-my-backyard fear of transferring Guantanamo detainees to prisons on American soil is not a new phenomenon. Mr. Obama made the promise to close Guantanamo one of his first as president, and Congress has sought to stop him continually since. What's changed, though, is the increased urgency for Mr. Obama, as his second term comes to a close, to exercise his wartime authority as commander in chief to close the prison unilaterally. He not only can take such action but he must if he is to safeguard our national security.