This handbook details an EU case law approach to the concept of discretionary eligibility within the context of public procurement. It provides examples from the jurisprudence of the Court of Justice of the European Union (CJEU) in order to provide insights into applicable discretionary power on the part of the contracting authority. The measurement of its tolerable range, as shown here, is directly related to the entire range of European law, and in particular to the general principles guiding its very own European spirit. Both EU and WTO grammatical interpretations are highlighted here as legitimized limits to the discretionary power exercised by public authorities.