This article argues that the principle of judicial economy belongs to the fundamental canons of international procedure – that is, those canons which are inherent in the judicial function and whose application should generally be ensured by the judge concerned, regardless of what the written procedural law establishes. This is particularly evident if one considers how often international courts and tribunals, precisely for reasons of judicial economy and departing from the duty to decide all points put forward by the parties (non ultra petita), enter into those issues alone which are necessary for the purpose of resolving the dispute and/or establishing the true state of the world (the so-called criterion of judicial limitation of the scope of the decision or absorption). Even though no provision requires it, each judge is in fact expected to operate in conformity with this criterion and to use it in a proper way; its misapplication may lead to reforming the decision or precluding its enforcement. The frequent use of the criterion at issue, on the other hand, supports this article's final contention, according to which judicial economy is an expression of judicial activism.