15First, it must be noted that the principal purpose of Directive 89/106 is to remove obstacles to trade by creating conditions which enable construction products to be marketed freely within the European Union. To that end, that directive specifies the essential requirements which construction products must satisfy and which are put into effect by harmonised standards as well as national implementing standards, European technical approvals and national technical specifications recognised at European Union level (see, to that effect, judgment of 13 March 2008 in Case C-227/06Commission v Belgium, paragraph 31).