First of all thank to all of you for participating to that debate. I just want to give some few comments that will either resume opinions, either complete some, either integrate practical perspective.

The research for a just use of violence:
Looking for a moral justification to war is indeed an old issue. The Hindu set rules forward in -1750 through the code of Manu. The Babylonians legislated on war in -1500 with the Code of Hammurabi. The Muslims stated that the use of chemical weapons and non discriminative weapons were forbidden as immoral after Constantinople siege…
The research for Just war is as old as war practice. Jus in bello and Jus at bellum are middle age notions. War is part of humanity and it is its practice that defines our humanity.
Separating military and civilian first as actors then as practices in war is important, just as separating military from humanitarian is. But it is limitative.
The separation between Humanitarian action and military action is based on the universal search of all to exclude parts of the populations from war into conflicts.

Unjust humanitarian action:
As Tom said, it is difficult to help people with blood on their hands. I experimented the same twisted feeling in my first mission in Kosovo as I was providing aid to Serbs. It feels really "strange" to remain neutral when having a toast in the name of the great Serbia and killing all the Albanian slaves...
An unjust humanitarian action could be partly defined on the choice: who you decide to help. This is a discriminative approach which is not in accordance with humanitarian doctrine/principles. It is also the military approach of humanitarian aid and leads to its militarisation. Does that mean it is an unjust action? I would be very glad to have both opinion (civilian and military or veteran) on that point.

Just humanitarian action:
The theories of Do No Harm is an important theory and difficult practice. It has been well pointed that most of experienced humanitarian workers, donors and other civilian actors in relief are aware of it.
Does that mean that being aware makes your action Just?
And even, looking at practices based on legal status as refugee, IDP... leads to discriminative actions led by civilian, targeting civilian, almost not integrated into military plans. Do no harm recommends to use a vulnerability approach. But is that sufficient? Or efficient? And is that Just?

Practical approach
But boundaries between military action and humanitarian action are getting thinner if not relegated to moral postures; as the distinction between military and civilian.
The actual doctrine in Afghanistan is to convince civilian that they have to choose a political master rather than one other.
In South Sudan, war was politically won through humanitarian action.
In North Kivu, military are using humanitarian aid to monitor and restrain military misbehaviours.
Humanitarian actors and humanitarian action is no more (if ever had) a hippie stuff. It is a complex civilian action into a complex military environment. What would be the limit to keep humanitarian action Just?
If humanitarian action allows providing direct security or support security action, is that still humanitarian action? And is that unjust?

The "Jus" in war:
Carl Schmitt exposed the limit of the Just War as an eternal unjust battle from a moral dictator that justifies on its victories the rightness of his cause.
He point was based on his experience of the nazi regime that can be seen as Evil but would have been seen as Good if they had won the war.
Is their such limits in humanitarian action? And what could be humanitarian limits?

I know, I am asking more questions. But I believe that answering to those questions is important for all of us that are participating to conflict and trying to provide protection to civilian populations.
If some points are not taken or misunderstood: please let me know. (I am human, that my strength and wickness.)