42Whilst the principle of legal certainty precludes a regulation from being applied retroactively, irrespective of whether such application might produce favourable or unfavourable effects for the person concerned, the same principle requires that any factual situation should normally, in the absence of any express contrary provision, be examined in the light of the legal rules existing at the time when the situation obtained (Case 10/78 Belbouab [1978] ECR 1915, paragraph 7). If the new law is thus valid only for the future, it also applies, save for derogation, to the future effects of situations which came about during the period of validity of the old law (see, to that effect, Case 96/77 Bauche and Delquignies [1978] ECR 383, paragraph 48; Case 125/77 Koninklijke Scholten-Honig and De Bijenkorf [1978] ECR 1991, paragraph 37; Case 40/79 P. v Commission [1981] ECR 361, paragraph 12; Case 270/84 Licata v Economic and Social Committee [1986] ECR 2305, paragraph 31; and Case C-28/00 Kauer [2002] ECR I-1343, paragraph 20).
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