Rückwirkung in grenzüberschreitenden Sachverhalten: Zwischen Statutenwechsel und ordre public

Retroactive Effect in International Matters, Change of the Applicable Law, and Public Policy. – While German law does provide for a detailed differentiation as regards retroactive effect in the domestic context (II.), retroactivity has rarely been discussed in transnational cases relating to civil matters. The national solutions cannot generally be transferred to the international level; instead, it is crucial to rely on the methods of private international law – in particular rules dealing with a change of the applicable law and with public policy. German private international law largely prevents retroactive effects from occurring through the methodology developed for dealing with a change of the applicable law (III.). Distinguishing between completed situations, ongoing transactions and divisible as well as indivisible long-term legal relationships, it is possible to ensure adherence to the principle of lex temporis actus. If the retroactive effect is caused by foreign law, it may violate public policy, which allows and calls for an adjustment (IV.). When determining whether a breach of public policy occurred in a case of retroactivity, it is necessary to consider the overall result of the application of foreign law rather than just the decision as to which foreign law is applicable. For guidance on whether such a result violates public policy, one has to look at the national principles dealing with retroactive effect.