OF THE FUNDAMENTAL PRINCIPLES OF COMMUNITY LAW . THIS PRINCIPLE REQUIRES THAT SIMILAR SITUATIONS SHALL NOT BE TREATED DIFFERENTLY UNLESS DIFFERENTIATION IS OBJECTIVELY JUSTIFIED .
17 AN EXAMINATION OF THE ADVANTAGES AND DRAWBACKS OF THE TWO LEGAL SITUATIONS WHICH HAVE TO BE COMPARED LEADS TO THE CONCLUSION THAT THE OBJECTION AS TO DISCRIMINATION CANNOT BE SUSTAINED IN REGARD TO EITHER OF THOSE SITUATIONS SINCE THEY CANNOT BE REGARDED AS BEING MORE FAVOURABLE TO ONE THAN TO THE OTHER CATEGORY OF WORKERS CONCERNED . THE FINANCIAL BURDEN OF THE BUYING-IN TRANSACTION WILL IN FACT BE HEAVIER OR LIGHTER FOR EITHER CATEGORY DEPENDING ON WHETHER THE PERIODS TO BE BOUGHT-IN ARE MORE RECENT OR FURTHER BACK IN TIME SO THAT THE FINANCIAL EFFECT OF THE RULES IN QUESTION IS NOT IN GENERAL MORE UNFAVOURABLE TO ONE THAN TO THE OTHER OF THE TWO CATEGORIES . THE VARIATIONS IN THAT FINANCIAL BURDEN FROM ONE INDIVIDUAL CASE TO ANOTHER ARE IN FACT EXCLUSIVELY THE RESULT OF THE OBJECTIVELY DIFFERENT FACTUAL SITUATIONS IN WHICH THE INSURED PERSONS CONCERNED MAY FIND THEMSELVES DEPENDING ON THE CHANGES AND CHANCES OF THEIR WORKING LIFE .
18 THE REPLY TO THE QUESTION SUBMITTED SHOULD THEREFORE BE THAT PARAGRAPHS 8 AND 9 OF PART C OF ANNEX V TO REGULATION NO 1408/71 , AS AMENDED BY REGULATION NO 1392/74 , MUST BE INTERPRETED TO MEAN THAT A GERMAN NATIONAL WHO HAS PAID CONTRIBUTIONS TO OLD-AGE PENSION INSURANCE IN ANOTHER MEMBER STATE AND WHO SUBSEQUENTLY WISHES TO PAY A POSTERIORI , BUT WITH RETROACTIVE EFFECT WITHIN THE MEANING OF ARTICLE 49A ( 2 ) ADDED TO THE ANGESTELLTENVERSICHERUNGS-NEUREGELUNGSGESETZ BY THE RENTENREFORMGESETZ OF 16 OCTOBER 1972 , GERMAN PENSION CONTRIBUTIONS IN RESPECT OF PREVIOUS PERIODS MAY BE REQUIRED TO PAY GERMAN CONTRIBUTIONS IN RESPECT OF PERIODS COVERED BY CONTRIBUTIONS IN ANOTHER MEMBER STATE AND THAT CONSIDERATION OF THE SAID PARAGRAPHS 8 AND 9 , AS THUS CONSTRUED , HAS DISCLOSED NO FACTOR OF SUCH A KIND AS TO AFFECT THEIR VALIDITY .
Decision on costs
19 THE COSTS INCURRED BY THE COMMISSION OF THE EUROPEAN COMMUNITIES , WHICH HAS SUBMITTED OBSERVATIONS TO THE COURT , ARE NOT RECOVERABLE . SINCE THE PROCEEDINGS ARE , IN SO FAR AS THE PARTIES TO THE MAIN ACTION ARE CONCERNED , IN THE NATURE OF A STEP IN THE ACTION PENDING BEFORE THE NATIONAL COURT , THE DECISION ON COSTS IS A MATTER FOR THAT COURT .
Operative part
ON THOSE GROUNDS ,
THE COURT ,
IN ANSWER TO THE QUESTIONS REFERRED TO IT BY THE BUNDESSOZIALGERICHT BY AN ORDER OF 12 OCTOBER 1979 RECEIVED AT THE COURT ON 7 DECEMBER 1979 , HEREBY RULES :
PARAGRAPHS 8 AND 9 OF PART C OF ANNEX V TO REGULATION NO 1408/71 OF THE COUNCIL OF 14 JUNE 1971 ON THE APPLICATION OF SOCIAL SECURITY SCHEMES TO EMPLOYED PERSONS AND THEIR FAMILIES MOVING WITHIN THE COMMUNITY , AS AMENDED BY REGULATION NO 1392/74 OF THE COUNCIL OF 4 JUNE 1974 , MUST BE INTERPRETED TO MEAN THAT A