1 . OBJECTION OF ILLEGALITY - PROVISIONS OF GENERAL DECISIONS WHICH MAY BE SO CHALLENGED - PROVISIONS CONSTITUTING THE BASIS FOR THE CONTESTED INDIVIDUAL DECISION ( ECSC TREATY , THIRD PARAGRAPH OF ARTICLE 36 ) 2 . ECSC - PRODUCTION - SYSTEM OF PRODUCTION QUOTAS FOR STEEL - DECISION NO 2794/80/ECSC - RETROACTIVE NATURE 3 . MEASURES OF THE INSTITUTIONS - TIME FROM WHICH THEY TAKE EFFECT - PRINCIPLE THAT THEY MAY NOT BE RETROACTIVE - EXCEPTIONS - CONDITIONS 4 . ECSC - PRODUCTION - SYSTEM OF QUOTAS - OBLIGATION OF THE COMMISSION TO CARRY OUT STUDIES JOINTLY WITH UNDERTAKINGS AND ASSOCIATIONS OF UNDERTAKINGS - LIMITS ( ECSC TREATY , ART . 58 ( 2 )) 5 . ECSC - PRODUCTION - SYSTEM OF QUOTAS - CONCOMITANT ADOPTION OF MEASURES CONCERNING IMPORTS FROM NON-MEMBER COUNTRIES - POWER OF APPRAISAL OF THE COMMISSION ( ECSC TREATY , ART . 58 ( 1 ))