This article places into question the scope of judicial control over the Prosecutor’s decision whether or not to investigate a situation. It addresses the on-going tensions between the Pre-Trial Chambers and the Prosecutor for the control of the procedure which will determine the stage of the initiation of an investigation. It commences with an examination of the Chambers’ approach to the authorisation of the Prosecutor’s request to commence a proprio motu investigation. Then, it critically analyses the lack of judicial mechanisms of control over the Prosecutor’s decision not to commence an investigation under Article 15. The second part investigates the judicial oversight of the Prosecutor’s decision not investigate referred situation. It analyses whether the Pre-Trial Chamber may reassess the factual allegations used by the Prosecutor not to start the investigation, and whether the Prosecutor has to comply with (strict) instructions provided by the judicial review.