There are in fact five different international courts in the Hague, and none of them has the right mandate for this job.
Going through them in the order that they were established: The Permanent Court of Arbitration doesn't take criminal cases; the International Court of Justice takes only inter-state cases; the Iran-United States Claims Tribunal is obviously not appropriate for the job; and the same goes for the International Criminal Tribunal for the former Yugoslavia.
The International Criminal Court at first glance seems the most obvious choice - its remit includes genocide, crimes against humanity, war crimes, and the crime of aggression. However a) it can only take cases where the alleged offences took place after 1 July 2002, which was less than a year before Saddam was overthrown, b) it can only take cases where the domestic courts are clearly incapable of taking the burden on (which indeed was arguably the case in Iraq, but someone has to make that determination, either the Iraqi authorities themselves or the UN Security Council), and most crucially c) it can only take cases from countries which have signed the Rome Statute setting it up, which notably do not include the United States or Iraq.
For an international prosecution process for Saddam Hussein to take place would have required an ad hoc decision either by the allies who overthrew him (which would have been even more obviously victors' justice than what we have had) or a decision by the UN Security Council (which would never have happened, as too many of its members, including some with vetoes, would have seen such a move as tantamount to complicity in Bush's war).
So an Iraqi judicial process was the best we were ever going to get; though it is reasonable to say that this judicial process is not a good advertisement for the idea that you can impose universal principles of justice by force.
Having said that, the verdict was inevitable. The sentence was not. Capital punishment is never right. (Even Christopher Hitchens gets this.)
