Case C-171/11: Judgment of the Court (Fourth Chamber) of 12 July 2012 (reference for a preliminary ruling from the Oberlandesgericht Düsseldorf — Germany) — Fra.bo SpA v Deutsche Vereinigung des Gas- und Wasserfaches eV (DVGW) — Technisch-Wissenschaftlicher Verein (Free movement of goods — Measures having equivalent effect to a quantitative restriction — National certification procedure — Presumption of compliance with national law — Applicability of Article 28 EC to a private-law certification body)