1 . FREE MOVEMENT OF GOODS - QUANTITATIVE RESTRICTIONS - MEASURES HAVING EQUIVALENT EFFECT - GRANT OF CREDIT TERMS FAVOURING THE PURCHASE OF DOMESTIC PRODUCTS - PRACTICE AMOUNTING TO A MEASURE HAVING EQUIVALENT EFFECT - INVALID UNDER NATIONAL LAW - IMMATERIAL ( EEC TREATY , ART . 30 ) 2 . MEMBER STATES - OBLIGATIONS - SUPERVISORY TASKS ASSIGNED TO THE COMMISSION - DUTY OF MEMBER STATES - COOPERATION IN INQUIRIES INTO WHETHER A MEMBER STATE HAS FAILED TO FULFIL ITS TREATY OBLIGATIONS ( EEC TREATY , ARTS 5 , 155 AND 169 )