Cuadernos de Derecho Transnacional (Octubre 2018), Vol. 10, Nº 2, pp. 579-596 ISSN 1989-4570 - www.uc3m.es/cdt - DOI: https://doi.org/10.20318/cdt.2018.4390 579 PARTY AUTONOMY AND THE LAW APPLICABLE TO THE MATRIMONIAL PROPERTY REGIMES IN EUROPE LA AUTONOMÍA DE LA VOLUNTAD Y LA LEY APLICABLE A LOS REGÍMENES MATRIMONIALES EN EUROPA ELENA ALINA OPREA Faculty of Law, Babes Bolyai University Cluj Napoca Recibido: 16.03.2018 / Aceptado: 12.04.2018 DOI: https://doi.org/10.20318/cdt.2018.4390 Abstract: In a private international law context refecting signifcant divergences between the ob- jective choice-of-law rules for matrimonial property regimes, the principle of party autonomy appears as a salutary solution, bringing certainty, predictability and simplicity, while satisfying also the spouses’ substantial interests. The study focuses on the rules devoted to this principle by the European legislator in the (EU) Regulation no 2016/1103, attempting to outline its regime and insisting, particularly, on its admissibility and on the limitations that accompany its practical exercise. Providing a suffcient fra- mework for discussion and helping to illustrate the implications of the European text, the rules of the Romanian Civil Code and of the 1978 Hague Convention on the law applicable to matrimonial property regimes will serve as a benchmark. Keywords: matrimonial property regimes, EU Regulation no 2016/1103, autonomy of will, electio juris agreements, states with more than one legal system, change of the applicable law. Resumen: En un contexto de derecho internacional privado que refeja divergencias signifcativas entre las reglas objetivas de elección de los regímenes matrimoniales, el principio de autonomía de las partes aparece como una solución saludable, aportando certeza, previsibilidad y simplicidad, al tiempo que satisface también los intereses sustanciales de los cónyuges. El estudio se centra en las normas dedicadas a este principio por el legislador europeo en el Reglamento (UE) n. ° 2016/1103, que intenta delinear su régimen e insistir, en particular, en su admisibilidad y en las limitaciones que acompañan a su ejercicio práctico. Proporcionar un marco sufciente para el debate y ayudar a ilustrar las implicaciones del texto europeo, las normas del Código Civil rumano y del Convenio de La Haya de 1978 sobre la ley aplicable a los regímenes matrimoniales de propiedad servirán como punto de referencia. Palabras clave: regímenes económicos matrimoniales, Reglamento (UE) no 2016/1103, auto- nomía de la voluntad, acuerdo de elección de la ley aplicable, estados con diversos regímenes jurídicos, cambio de la ley aplicable Summary: I. Introductory aspects – importance of the party autonomy. II. Partial unifor- mization of PIL for matrimonial property regimes in the EU Member States. 1. EU Regulation no 2016/1103 - introductory issues. 2. Limited uniformization among the EU Member States. 3. Universal application. III. The spouses’ limited freedom to choose the applicable law. 1. Option in favour of the habitual residence law. 2. Option in favour of national law. 3. Dual nationality. 4. Di- fferences between the Article 22 of the Regulation and the corresponding texts from the Romanian Civil Code or the Hague Convention. Implications. IV. Electio juris and States with more than one legal system. V. The unity of the chosen law. VI. Consent and substantial validity of the choice-of- law agreement. VII. Exteriorisation of the parties’ choice and the law governing the form of the electio juris agreement. VIII. The moment of choice. IX. Change of the chosen law. 1. Admission of