Sic transit gloria mundi
One of my favorite Greek mythology stories is the one of Uranus and Cronus. As the ancestor of all gods of the Pantheon, Uranus for a long time had no rivals. He was the personification of the sky and the mate of Gaia (the Earth). Their children were the Titans. Since Uranus was jealous of the future power of his children and feared he would lose his command to them, he threw them in the underworld. An angered Gaia shaped a great flint-bladed sickle and asked her sons to castrate Uranus. Only Cronus, youngest of the Titans, was willing: he ambushed his father and emasculated him, casting the severed testicles into the sea. From the semen which spilled from Uranus onto the Earth several other divinities sprang forth.
Cronus re-imprisoned his siblings in Tartarus, and ruled like an absolute monarch. The period of Cronus’ rule was called the Golden Age, as the people of the time had no need for laws or rules; everyone did the right thing, and immorality was absent. Eventually, Cronus learned from Gaia and Uranus that he was destined to be overcome by his own son, just as he had overthrown his father. He attempted to avoid this fate by devouring his children. Only Zeus, through the deception of his mother, escaped to eventually dethrone Cronus and give rise to the multitude of gods populating the Greek Pantheon and become its ruler.
Now, think of the International Court of Justice as a sort of international judicial Uranus/Cronus; the idea of international rule of law based on courts as Gaia; and the multitude of international judicial bodies populating the contemporary scene as the Titans. The similarities with the myth are many.
Much like Uranus and Cronus, the World Court for long it had no rivals. For much of its history, the only potential contender was the Permanent Court of Arbitration. But the PCA was neither permanent nor a court, and, in any event, had already been shadowed in the 1920s by the establishment of the PCIJ.
A host of other international courts arose out of a rebellion and mutilation. They were born either because the ICJ was not considered a desirable forum (→the ITLOS), or because the ICJ was limited to states only (→the human rights tribunals), or because it could dispense the kind of justice needed (→ criminal tribunals); or because more specialized and focused bodies were needed (→WTO AB, ECJ, etc.). In other words, they were all born either out of dissatisfaction with the ICJ or because of its inadequacy.
In a way, these offspring were born to overtake it. Like the Titans, these younger, more dynamic entities are all the children of the same ideas that gave birth to the World Court almost a century ago: an international rule of law. They are all siblings.
Like Uranus and Cronus, the ICJ would like to confine them to the underworld of international law, keep them out of the ethereal world of customary international law and the general principles, of International Law with capital I and L. Like the father and grandfather of all gods, it considers itself first among equal gods (primus inter pares), but first nonetheless. It frets at the idea that some other international court might develop its own canons of treaty interpretation or might understand international responsibility differently. Yet, these offspring are taking on their fathers. They dare to rebel, they snub the Peace Palace, emboldened by their compulsory jurisdiction (unlike their emasculated ancestors). They go their own ways, do not bow or defer to the World Court and act and think faster, more effectively and, crucially, independently.
There is really no reason to get too exercised about the International Court of Justice. There is no reason to try to expose it many limitations and try to knock it down its haughty pedestal. It is already passé, the vestige of a bygone Golden Age. The world most important cases (by import, impact, resonance and any other criteria you might chose) are already decided elsewhere. As new generations of scholars are coming to age, and they look besides and beyond the case law of the ICJ to ascertain the content of international law, the World Court is going to lose its centrality to the international legal discourse (and be less likely to obsess those who wish to hasten its oblivion). Look at the demographics of a colloquium on international criminal courts, the WTO or the ECHR and then compare to that of a meeting on the ICJ. It is obvious where the future is.
Traditionally, Papal coronations are thrice interrupted by a barefoot monk holding a pole to which is affixed a burning piece of flax. After the flax finishes burning, the monk announces, “Pater sancte, sic transit gloria mundi” (holy father, thus passes the glory of the world). This is meant to remind the Pope that, despite the grandeur of the ceremony, and the long history of the office, he is a mortal man. Perhaps a barefooted clerk (one of those Julian would not like to see hired) might perform the same function at the Peace Palace.