Innovations in case law have traditionally always had retroactive effect also, first on the case in question, and therefore on past conduct, and then, to the extent that authority attaches to the precedent or it is at least followed in practice, on other cases subsequently heard, although the conduct involved here also preceded the declaration of the new rule. Justice Holmes, in a dissenting opinion of 1910, wrote: “I know of no authority in this case to say that in general state decisions shall make law only for the future. Judicial decisions have had retrospective operation for near a thousand years”.

It is fairly certain that Justice Holmes had the Common Law world in mind, but the picture would not be different if we looked at the situation elsewhere. In France as well, for instance, the rétroactivité des nouvelles jurisprudences has been considered as une infirmité du système jurisprudentiel.

Nevertheless, it is a fact that the situation excites some consternation among lawyers and the public, which is particularly strong in those matters where retroactivity is singularly severe in its effects and the legislature normally refrains from imposing it, although not forbidden to do so under constitutional principles (laws being interpreted and applied non-retroactively in the absence of any express provision in this regard) and in those instances where there was reliance, explicit or presumed, by the parties on the rule which is subsequently abandoned.

The Rules of Court which the International Court of Justice adopted in 1946, on the commencement of its existence, were essentially a reproduction of the Rules of Court adopted by the Permanent Court of International Justice on March 11, 1936 with such alterations as became necessary after the changes incorporated in the new Court's Statute, in comparison with that of the Permanent Court. When the Court adopted those Rules it did so with the intention of undertaking a more thorough revision after more experience of the judicial function had been acquired. Since then, the Court has had the matter under review, but for over twenty years nothing concrete has emerged.

The Court has had a rough passage in this period. This is demonstrated by insufficient judicial business, bitter debates on its role in the United Nations both in connection with advisory opinions and in connection with the inclusion of jurisdictional clauses in multilateral treaties drawn up in United Nations meetings, widespread mistrust of the Court as an institution and of judicial settlement as a mode for the pacific settlement of international disputes, and a general malaise attending everything to do with the Court.

It is well-known that Jewish law forbids ona'ah “overreaching”; that is to say: the act of wronging a person by selling him an article for more than its real (market) value, or, conversely, purchasing from him an article for less than its real value (M. Bava Mezia 3.4, seq.). According to (anonymous—stam) Tannaitic halacha (law), the right to claim against ona'ah was always in the hands of the injured party, and whichever side constituted the injured party (be it the vendor or the purchaser), that side had the right to choose either to declare the transaction void, or to make up, or receive the difference (T. Bava Mezia 4.3). Another view, that of R. Judah (ha-Nasi, flor. c. 170–220), is however recorded. R. Judah states that regardless of which side is the injured party, the choice as to whether to annul the transaction or to settle the difference always lies in the hands of the vendor (B. Bava Mezia 50b, Y. Bava Mezia 4.3). This (minority) view was rejected in the Amoraic period by the great Palestinian scholar R. Johanan (flor. c. 250–79), so that the later halacha follows the anonymous (majority) Tannaitic ruling (Y. Bava Mezia 4.3).

The degree fixed in Tannaitic sources for ona'ah was one-sixth (M. Bava Mezia 4.3, 7; T. Bava Mezia 3.9). That is to say, anything less than one-sixth above or below the market price was not considered ona'ah, and the transaction was valid, while one-sixth or more constituted ona'ah, invalidating the transaction, unless the injured party (stam) or the vendor (R. Judah) agreed to settle the difference.