Milosevic's death and the future of the ICTY

Today I attended a discussion on Milosevic. Nothing what I heard there was new although I did find out that Voislav Sesel Vojislav ?e?elj is being tried not primarely for his activities as a paramilitary commander rather than a radical Serbian politician.
Whatever can be said about Milosevic, one things seems to be clear in the short-term perspective. His death is a devastating blow to the credibility of the Hague Tribunal as it underscores its procedurial impotence (Milosevic had been in custody for four years and there was no end in sight when he died) and dubious legal standings.
I'm not a lawyer, so perhaps my analysis is rather naive but from what I have understood about his case it rested on the notion of 'command responsibility' which itself is based on 'customary international law' (read more about it here).

To me the whole notion of 'customary' law is itself dubious but even in the text it is stated that

By 1977 the doctrine of command responsibility was accepted as customary international law and was codified in the Additional Protocol I to the Geneva Conventions, relating to the International Armed Conflicts [emphasis added].

So it seems that the concept would not be applicable to the civil war in former Yugoslavia. However below it states that

It should be noted that international law recognizes the principle of command responsibility both in international and in internal armed conflict.

So when did it happen exactly?