The monograph is based on a doctoral thesis of the author, in which she presents an incisive analysis of philosophical, theoretical and practical aspects of the liability of private persons for breach of community law. The first part of the book attempts to analyze the notions of effectiveness, direct applicability and enforceability of European primary law. Hence, the European directives and the problem of horizontal effect thereof are intentionally left out of the scope of the analysis. The rules on State liability for breach of Community law are set against the historical and constitutional background. The second part, entitled "The European ius commune", addresses all aspects of civil liability ensuing from a breach of primary Community law by a private party, in particular the premises of liability. The inspiration is taken from the Courage doctrine as developed by the ECJ. The author also examines various documents produced by European groups engaged in projects on the harmonization of civil law (in particular of tort law). Adamczak-Retecka undertakes formulating the premises of the liability under the Polish civil code. She correctly concludes that the liability should be based on fault and can be established based on the existing tort law. In the third part the author outlines the mechanisms of the enforcement of claims for compensation based on violations of European law by private parties (including procedural as well as private international law aspects).