Targeting and the Just War Theory

"Megan McArdle is attending a conference in Aspen with Stephen Carter, who is giving a talk on proportionality under the Just War theory.

I can't tell how much of this is Carter and how much of this is McArdle, but I had to respond to this passage from McArdle's post:

Carter is now discussing the problems inherent in the twin principles enshrined in both just war theory: proportionality and discrimination.

Proportionality means that you should use the method that will produce the fewest casualties. But taken to its logical extreme, this would dictate that commanders are obligated to take an objective in a way that kills 100 of their guys and 200 of their guys, instead of in a way that kills 10 of your guys and 1,000 of their guys. Indeed, some proponents of international law do argue this. But it is morally thorny (and you can then start asking what minimizes net casualties over the course of the war, rather than current ones). Moreover, if you have a theory of war that tells commanders they should sacrifice large numbers of their men to save the enemy, you will have a theory of war that is never applied to an actual war.
The problem of discrimination is also difficult. We think of just war theory as telling us that you can't target civilians, but in fact it says you can't target "non-combatants"--that's why you can't shoot prisoners. But this becomes extremely difficult. Who is a non-combatant? The cooks? A general back at headquarters? Infantry troops who happen to be asleep?

My response (also in her comments:)

I hope Carter is a little smarter than to use the examples given here. For example, there is NO doubt, NONE, that a general back at headquarters is a combatant. There is NO doubt, NONE, under international law, the law of land warfare, or anywhere else, that infantry troops asleep are noncombatants. There NEVER has been, EVER. There is NO doubt, NONE, that cooks in the direct service of an army at war are combatants."
CouterColumn

"There is NO doubt, NONE, under international law, the law of land warfare, or anywhere else, that infantry troops asleep are noncombatants."

That actually surprised me. Did I read that right?
Infantry troops are not targets if they are sleeping?

How do you go about determining if they are asleep or not before attacking?