The article considers the principal legal implications of the key, general legislative framework on services regulation, the Services Directive (Directive 2006/123/EC on services in the internal market), exploring, several years since its implementation deadline and in view of the emerging litigation, the resilience of this regulatory endeavour at the heart of the EU’s economy. In particular, the present contribution analyses focal aspects of the directive, especially as interpreted by the Court of Justice of the European Union, through the prism of the directive’s objectives of legal certainty, acquis compatibility, and synchronization. In doing so, the study evaluates the contribution of the directive to positive harmonization and its interaction with the negative integration regime for the completion of the internal market in services.