A jail suitable for Gitmo detainees is supposedly in Alexandria, VA. A move here will relieve the U.S. of the international burden that Gitmo represents. However, I can see Islamists seeing this as a victory. Having their captured men near Washington D.C.? This is next to and inside the political capital of the infidel enemy. This will give them a much greater status than we should give. Despite assurances to the contrary, politics will play more of a role here, distorting the importance of issues.
Jail is NOT where we want to place the 21st century versions of the pirates of the 16th century. They were generally hung from the nearest yardarm. Today we cannot do this. An island with complete isolation is about the closest way without executing them. Placing them into our jail system opens us up to additional assault from within. Jails are ALWAYS filled with people with revolutionary views.
The idea behind a jail is to hold someone who is dangerous and rehabilitate him or her to the point where they can be released into the public and do no more harm. A few of the detainees at Gitmo may be rehabilitated, but the majority is not. It would be like taking Japanese soldiers in 1944 and attempting to rehabilitate them while the war was still going on. The point is that these men will use the opportunity to convert others to their cause. And jail is the perfect place for them to obtain a receptive audience.
If anyone believes that we can control this, they do not fully comprehend the commitment these men have, nor of the support around the world this effort would be receiving. Remember how Germany assisted Lenin in his move back into Russia? They needed him to stir up trouble for Russia during World War I. He helped trigger the Russian Civil War and Russian withdrawal from World War I altogether. It almost won the war for Germany. It caused incalculable problems in Russia for generations afterward. If it can be done, our enemies today will not hesitate to do it. We will be making a mistake to assist them in anyway.