The book tries to identify the main contours of unjusticiability and non-justiciability from an historical and comparative perspective distinguishing between common law world and civil law tradition. In the light of a general overview, the aim of this publication is to reflect on the utility of paving the way for a much wider approach to unjusticiability. More precisely, some scholars have recently suggested that such a notion could embrace all the situations where a court does not decide a case, so that it is impossible for the plaintiff to have the case decided by a court. A first category covers the situations where the court refuses to judge because it does not want to judge. A second category is related to all the cases where there is an impossibility to reach a decision. Any case where the judge cannot or does not wish to make justice—si iudex non facit iustitiam—continues to indicate a series of new (and old) questions.