Most modern writers accept that general principles are of secondary importance to custom an treaties, to be utilized only where the two primary sources are unable to provide a solution. It is not clear whether general principles refer to those of the international legal system or those of municipal legal system. Hence, there is no restraint on the principles, which may be applied.

A more controversial question is that of the doctrine of equity, or fairness. Equity could form part of a judgment but only equity, which both parties have recognized as applicable in the case. The I.C.J. declared that equity, as a legal concept is a direct emanation of the idea of justice. However, principles of equity cannot overturn accepted legal rules.