These days, the battle lines are drawn between ideologies rather than countries, yet Article 51 of the United Nations Charter grants nations the inherent right to self-defense. The citizenship of the fighters is irrelevant with this relatively new kind of warfare -- at least until someone kills a dual American citizen (like Anwar al-Awlaki, the Forrest Gump of contemporary Islamic terrorism) and human-rights groups try to make the victim sound like Donny Osmond. When these activist groups start trying to wrap up warfare in legal red tape, it becomes evident that we can't fight these fourth-generation, guerilla-style, ideologically driven wars using the outdated framework of old-school, second-generation nation-state conflicts.
What if the next Osama bin Laden happens to have American citizenship? Should he be exempt from the consequences of military action simply because he's an American? Should he be allowed to lawyer up from a foreign battlefield just because his American citizenship is supposed to confer an innate right to by-the-second billable hours? Or instead, and in very defined instances, should he just be vaporized?
This is the sort of scenario for which the Justice Department and the White House appear to be laying the groundwork, and the DOJ memo is clearly just a start in the development of new warfare parameters.
Ideologically based fourth-generation warfare (4GW) is finally attempting to play catch-up with the development of a long-overdue new framework. This isn't about some nefarious plot to kill everyday Americans -- it's about government legally covering its behind for every possible 4GW eventuality.
The subject of drones being the preferred new tools of warfare in an era of heightened sensitivity to military casualties is an entirely different matter of debate.
If, as an American citizen, you steer clear of places like Pakistani terror training camps, you'll be just fine in any case.