‘There is nothing new under the sun’, said Ecclesiastes; and this is broadly true of inter-State arbitration (ISA), though some recent developments have perhaps thrown certain issues into greater prominence. So I shall here provide a fairly standard account of the factors which lead States to choose or refuse to arbitrate with other States. In the course of doing so, I shall allude to some issues that have recently arisen. I will consider: whether ISA is even available in a given situation; the need for consent; and the many pros and cons of this form of dispute settlement.

It is a particular pleasure to contribute an essay on the sources of international law to this Festschrift for Sir Robert Jennings in recognition, not only of his distinguished contributions to this topic both as an academic and as a judge, but also of personal acts of kindness.

Every case in the World Court involves the sources of international law in some form, because every case requires an investigation of substantive or adjective rules whose existence and legal effect ultimately depends on their having been created by one of the means recognized as apt for this purpose. Even if one eliminates cases where there was no issue as to the status of the rule, but only as to its content, in the fifty years since the International Court of Justice was established it has had very many occasions to make rulings pertinent to our topic. In the space available here, any review of its contribution is inevitably summary and impressionistic.

The ICJ has not attempted to elaborate a theory of the sources of international law or attempted to catalogue them. This is hardly surprising: its function is to decide the particular disputes before it, not to elaborate general theories or to decide questions that are not in issue.