This article undertakes an inquiry into the jurisprudence of the Community courts (now the EU courts) discretionary powers and the scope of judicial review, revealing that although they are aware of the issue, they do not address it in depth and leave crucial things unsaid. On the basis of this inquiry, a framework is presented in which discretion and scope of judicial review can be analysed as an issue of horizontal division of tasks and powers between the European courts and the other EU institutions and therefore as part of the general principle of institutional balance. For that purpose, discretion is defined as the administrator’s competence to decide with highest authority about the application of the law to a specific fact pattern resulting from both the absence of precise statutory predetermination and subsequent de novo decision by controlling administrative courts. While the institutional balance between the courts and the other institutions is primarily determined by the attribution of tasks and competences to them by primary and secondary EU law, it unfolds normative power whenever these provisions leave gaps or uncertainties. It is argued that in such cases functional criteria can be utilized to “fine-tune” the institutional balance. The institution that is best suited in terms of organization, composition, function, legitimation, and procedure shall then decide a certain aspect with highest authority. Finally, this approach is applied to the joint application of Articles 101, 102 TFEU to specific cases by the European Commission and the General Court, trying to establish what complex economic facts are and give reasons why the GC must defer to the Commission whenever those facts have to be appraised.