From the Founding right up until the still-quaking bombshell of Hamdan v. Rumsfeld, issued at the end of the Supreme Court’s term in late June, the primary imperative of national government was to protect the security of the governed from hostile outsiders. The Framers, however, had an ingenious gloss on this venerable first principle. In the great American experiment in republican democracy, this power of self-preservation—what Justice Felix Frankfurter, in another era of grave peril, called “the most pervasive aspect of sovereignty”—would repose only in those political actors directly accountable to the people whose lives hung in the balance.

The arrangement made exquisite sense. On the one hand, if the public’s representatives were insufficiently attentive to national security, those with the most at stake could vote them out of office. On the other hand, if public officials failed ...