1 . MEASURES ADOPTED BY THE COMMUNITY INSTITUTIONS - REGULATIONS - APPLICATION RATIONE TEMPORIS - PRINCIPLE THAT MEASURES MUST NOT BE RETROACTIVE - EXCEPTIONS - CONDITIONS 2 . COMMON CUSTOMS TARIFF - IMPORTATION FREE OF CUSTOMS DUTIES - ' SCIENTIFIC INSTRUMENT OR APPARATUS ' - CAPACITY TO CARRY OUT ' SCIENTIFIC ACTIVITIES ' - CONCEPTS ( REGULATION NO 1798/75 OF THE COUNCIL , ART . 3 ( 1 ) AND ART . 3 ( 3 ), AS AMENDED BY REGULATION NO 1027/79 )