RFID tagging terror suspects

So we have a slew of terror suspects in Gitmo and in prisons in Iraq. Rather than use questionable interrogation techniques on them to obtain information I have another idea.

RFID tags are being used to track everything from the items we buy to cargo shipments and even cash. Why not tag these terrorists and simply let them go? They will likely go back to their terror cells thus aiding us in locating caches of weapons and other terrorists.

The terrorists could be tagged via a simple, out-patient type procedure where the tiny RFID tag is placed under the skin. The terrorist would need to be sedated while the procedure is done and it would have to be done in a way that they would have no way of knowing that in fact they had been tagged.

What do you think?