The problem with drones is that using them to kill people not on the battlefield per se doesn't fit neatly into our existing categories of "war" and "police work."
This may seem like a new problem, but it isn't. It's a problem that reappears every time the rules of the game(s) change.
Take the American Revolution. The Brits thought we were war criminals because we didn't always meet them on the field of battle--where their highly disciplined Redcoats could make up for the slow firing pattern of the flintlock musket by arranging to have one row firing while the next row was reloading, and the like.
So instead our soldiers would sometimes not meet them on the "field of battle" where the Redcoats had an advantage, but instead stow snipers in the trees along the routes back to the barracks or tents or whatever, and shoot them in the back as they passed by.
And many Southerners thought General Sherman was a war criminal because he attacked the South's ability to feed & otherwise supply its troops--in the process put many Southern civilians in starvation conditions.
To which accusation Sherman famously replied "War is hell." In the judgment of history, Sherman did the nation a favor because he cut off the South's army at the knees, shortening the war. And thus he even did the South a favor.
And the recent effort to grant women the ability to serve in combat featured the argument that women were already serving in combat--just not getting credit or advancement for it--because what and where is the battlefield today?
The "battlefield" is everywhere and everywhen anyone or any group waging war on our country and its people is preparing to attack us or actually attacking us.
War is no longer just between nation-states. With the Islamofascist movement, our enemy can be anywhere, with no fixed capitol to defend, no land to defend, which, if lost, means the enemy is defeated. 9/11 was planned in Hamburg Germany operationally, and in Afghanistan strategically, and carried out by Saudis for the most part.
Now when that planning is taking place in another country that controls all its territory, has diplomatic relations with us, and is board with our efforts to combat terrorists, then police work is usually the best way to nab them. That was the case with Germany--less so with Saudi Arabia for what should be obvious reasons.
However, Afghanistan was another case. The Taliban controlling it were no friends of us but they were just hosting the Islamofascists who attacked us--who, when defeated, just moved their base of operations elsewhere.
Then what? Our enemies are operating in countries that are either completely hostile to us or which are not in control of the territories where our Islamofascist enemies are operating.
That leaves us with three choices, basically:
1. Invade, in force, countries that aren't at war with us but in whose territory groups at war with America are operating.
2. Concentrate solely on defensive measures within our own territory and rely on other countries' police forces within their territory.
3. Carry out military incursions by special forces, drones and the like.
There's one other option: withdraw completely from all territory that Islamofascists want us out of, and/or convert en masse to Salafist Islam. I won't comment on this option further.
The people who call drone-based assassinations "war crimes" divide between those on the Left, who obviously want Option 2, and those on the Right, who divide between NeoCons who want Option 1 and Isolationists (like Pat Buchanan and Ron Paul) who seem to waffle between Options 2 & 3 (though for many their real position appear to be simply opposing anything Obama does, even if he's doing exactly what their guy was doing just a few years ago).
The flaw in Option 2 is that Pakistan's police force mostly hates our guts and will do nothing to help us--in fact they'll mostly help our enemies; Iran's police force is actively helping terrorists who want to attack us and our allies; Somalia's police force doesn't control a lot of Somalia, and ditto for Yemen, and ditto for the Texas-sized north of Mali, and so forth.
So in the case of the places where Islamofascists who have declared war on us are mostly headquartered and operating training camps, Option 2 restricts us to police work within our borders. I doubt many Americans find that acceptable.
Nor do many Americans support going to a full war footing, with a draft and rationing and the whole WWII thing, which is what it would take to invade all the wild places where our enemies are--Pakistan, Yemen, Somalia, Mali, Iran, Afghanistan, Iraq and more, simultaneously (since otherwise they'd just go where we aren't).
The notion that the Islamofascist declaration of war on America--on every single American citizen and every bit of our territory and assets--is exactly the same as a criminal gang planning a bank robbery--is ludicrous.
The problem isn't the drones, but the simple-mindedness of ideologists who think "war" still means what it meant during WWII (which it didn't even then, in fact). Not just simple-mindedness, but also the tendency of lawyers to think everything is a legal issue, as in "to a hammer, everything looks like a nail."
We are in a war not of our choosing, with an amorphous, shifting, many-headed enemy that is supported by a number of countries but is not those countries, and which can't be defeated via military invasion of any one or two or three or four of those countries.
It's a war of shadows. Our drones operate out of sight. Our special forces work in the night. They sometimes kill civilians because civilians are ALWAYS killed in wars--the wonder is that we kill so few civilians, and so many fewer civilians then if we were carpet-bombing the areas in question, and so many fewer than when we started out with drones some years ago.
Sometimes drone pilots will loiter over an enemy force for hours, waiting until they can get a clear shot with no civilians nearby. Many drones fly slowly and quietly at pretty high altitudes, with much longer dwell time airborne than manned craft can sustain.
And of course unlike the Islamofascist enemies, we don't target civilians as they do--and they murder vastly greater numbers of civilians that we do in drone strikes and special forces operations. But every time a drone strikes, the enemy publishes grisly photographs of dead babies on the Net, which they claim we killed instead of them. Sometimes--most times--they're lying, but Arab Joe Lunchboxes have zero training in critical thinking and mostly have been indoctrinated from birth to hate us.
So drones and special forces incursions in areas where police forces won't or can't collaborate with us are the least bad of our options.
Don't let anyone deny this without describing what they think we should do instead. I submit that most of what they propose is patently silly--and anachronistic as well.
Calling drone strikes "war crimes" is the same as the Revolutionary Era Brits calling us war criminals for shooting their soldiers--and those red and white uniforms were a great aid for targeting--from concealed positions by sharpshooters.
The "war crime" would be our nation's government not acting to protect us--protect us from people who are not at war with our armed forces--they're at war with every single one of us.