Avatar:
I'm asking in terms of law and justice.
I'm not aware of how the law works if countries do not recognise jurisdiction or if the ICC has none.
In such cases what are the appropriate channels, what is the law?
Can a trial be conducted in absentia? Can the ICC look at the evidence and reach conclusions even if the parties cannot be held accountable? What is the right legal procedure?
Nothing will be done.
International law is built on the mutual consent.
You can't try a country without it agreeing with it.
However there are peremptory norms of international law also called jus cogens which prohibit aggression.
Aggression according to a simplyfied definition is a military intervention if that isn't an act of self defence, or is not supported by the UNSC.
International law doesn't allow self defence before the act of aggression or at least knowledge that such an attack is imminent and grave.
In the case of Iraq it wasn't imminent. USA occupied Iraq by military force.
There were countries who supported it.
According to international law these countries have committed war crimes and it is in the interest of all international community to make sanctions against these countries, even more, it's an obligation erga omnes.
However International law mostly works only when everything is fine (daily routine) or the offending party is a weak one.
In this case the offending party is an incredibly strong one. Nobody has the political will to enforce the law against that party, because nobody has enough power and the consequences would not be favourable to those enforcing the law.
So they keep mostly silent about it and nothing will be done.
Ethical, not really, but c'est la vie.