Private international law smoothes the edges of civilian law and common law thanks to its specific legislative and technical structure. Conflict-of-law rules are considered to be neutral, and therefore more appropriate for unification, than substantive rules because countries are prepared to surrender their own individual solutions for the sake of uniform international or supranational regulation. This is evident in the successful unification of conflict-of-law rules at the global and European Union levels, as compared with the less common partial unifications of substantive rules. The paper illustrates several examples of unilateral legal acts in the European space, how diverse may be their substantive qualification in different legal systems, and what impacts these substantive differences may have upon the determination of the applicable law for obligations under European conflict-of-law rules. From the perspective of the conflict of laws, an issue remains open regarding what approach should be taken where a uniform legislative instrument – namely a European Regulation – fails to include a particular institution or act either expressly or impliedly.