Conflict of Laws in International Marriage: Divorce and Succession Under Strain

Imagine: you live in Saint-Julien-en-Genevois, a stone's throw from the Swiss border. You married a Swiss national in his country fifteen years ago. Today, separation is inevitable. But which law applies to your divorce? French law, where you reside, or Swiss law, where you married? The question is explosive, because the matrimonial property regime, maintenance payments or child custody can change completely depending on the answer.

This thorny issue of conflict of laws in international marriage has just been decided by the Rennes Court of Appeal in a judgment of 1 October 2024 (Case No. RG 21/08936). Its verdict? It provides keys to binational couples, but also to heirs when a death occurs after a life shared between two countries.

Before delving into the details, remember the essentials: if you have not expressly chosen the law applicable to your marriage or succession, it is the European and international rules that designate the law of the couple's last common domicile. A simple principle, but exceptions that can change everything.

The facts: a story like many others

Mr Y, originally French, and Mrs Z, Swiss by birth, married in Geneva in 2005. They quickly settled in Saint-Julien-en-Genevois, on the French side, where they lived peacefully for ten years. Two children were born. Then, in 2018, discord set in. Mrs Z returned to live in Geneva, while Mr Y remained in the family home in Saint-Julien. In 2020, Mr Y filed a divorce petition before the Annecy Judicial Court.

Problem: Mrs Z contested the jurisdiction of the French court. She argued that the marriage was celebrated in Switzerland, that the spouses had their last common domicile in Switzerland (in her view, because they lived in France but with strong Swiss ties) and that the applicable law should be Swiss law. Mr Y, for his part, wanted French law, which is more favourable regarding compensatory allowance (post-divorce maintenance).

The Annecy court declared itself competent but applied Swiss law. Mr Y appealed. The Rennes Court of Appeal – competent for appeals from western courts, but here seised due to special rules – examined the case. After months of proceedings, the judgment was delivered: the court confirmed the jurisdiction of the French court, but set conditions for the applicable law. Explanation.

The reasoning of the court – analysed

The magistrates of the Court of Appeal first rely on Regulation (EU) No 1259/2010 of 20 December 2010, known as 'Rome III', which uniformises conflict-of-law rules on divorce in Europe. Its Article 8 provides that, in the absence of a choice by the spouses, the applicable law is, successively: 1) the law of the last common domicile of the spouses (if one still resides there); 2) the law of their last habitual residence (if one still resides there); 3) the law of the State of which they have common nationality; 4) the law of the forum (the law of the court seised).

The court recalls that the concept of 'last common domicile' must be assessed concretely: it is the place where the spouses have lived together in a stable and habitual manner, with the intention of fixing the centre of their family interests. In this case, the couple lived in Saint-Julien-en-Genevois for over ten years. Mrs Z worked in Switzerland, Mr Y in France, but their children were schooled in France and the family home was in France. The court concludes that the last common domicile is in France. Therefore, French law is applicable, contrary to what the Annecy court had held.

Attention: this is not a reversal, but a strict application of the criteria. The court insists that Mrs Z's Swiss nationality is not sufficient to exclude the application of French law. It also confirms that the French court has jurisdiction (Article 3 of the Brussels II bis Regulation), because the defendant (Mrs Z) resides in Switzerland, but the petitioner (Mr Y) has resided in France for more than one year before the petition.

A crucial clarification: if the spouses had made an express choice of law (by marriage contract or afterwards), that choice would prevail. But in the absence of such an agreement, objective criteria dominate.

What this changes for you – concretely

If you are in a international marriage situation, this decision has three major implications.

For couples going through divorce: do not rely solely on your own sense of belonging. If you have lived in France with your spouse for several years, French law will likely apply, even if you are a foreign national. Example in Annecy: a Franco-German couple living in Annecy for 8 years, the German wife files for divorce before the French court. Without a marriage contract, the compensatory allowance will be calculated under French law (generally higher than under German law).

For international successions: the judgment does not directly deal with succession, but the reasoning applies by analogy. Regulation (EU) No 650/2012, known as 'Successions', provides that the applicable law is that of the deceased's last habitual residence, unless a choice is made. If a Franco-Swiss couple lived in Saint-Julien-en-Genevois and one dies, the succession will be governed by French law, even if the deceased was Swiss. Consequence: inheritance tax may be very different.

For spouses wishing to plan ahead: you can choose the law applicable to your divorce or succession by an express declaration. For example, a marriage contract in France, or a 'succession pact' in Switzerland. But beware of formalities: the choice must be made knowingly and comply with the form rules of each country.

Four tips to avoid this type of dispute

• Make a marriage contract: if you are in a binational couple, sign a marriage contract before a notary. You can choose the law applicable to your divorce (e.g., French law) and the matrimonial property regime. This cuts off any challenge.
• Declare your tax and family domicile consistently: ensure that your tax residence, administrative address, your children's school address, etc., are aligned. A contradiction (Swiss ID card but life in France) can be exploited by the other party.
• Anticipate succession: if you own property in France and another in Switzerland, draft a will specifying the law applicable to your succession. Use the forms provided by the European regulation. A notary specialised in international law will help you avoid conflicts of laws.
• Keep evidence of your life together: bills, employment contracts, school registrations, etc. In case of a dispute, these elements demonstrate the location of your common domicile. Do not neglect translating documents into French if necessary.

Further analysis: related case law and developments

The decision of the Rennes court follows a line of recent judgments. For example, the Court of Cassation, in a judgment of 12 January 2022 (No. 20-18.456), had already specified that the 'last common domicile' is assessed at the time the divorce petition is filed, not at the time of de facto separation. The Rennes court adopts this analysis. Another notable decision: the CJEU, on 16 July 2020 (Case C-173/19), held that the choice of the law applicable to divorce can be made implicitly, but only if the spouses have clearly manifested their intention. In this case, there was no such thing.

The trend is therefore towards European harmonisation of the rules, but with great importance given to the facts. French judges remain attached to the reality of daily life rather than formalities. This means that for couples living near borders (such as in Saint-Julien-en-Genevois or Annecy), it is crucial to document their territorial anchoring well.

In the future, the 'Brussels II ter' Regulation, applicable since 1 August 2022, further strengthens the jurisdiction of the court of the child's habitual residence for custody, but for divorce proper, Rome III remains the reference. Practitioners await full harmonisation, but until then, each case turns on its details.

Summary and next steps

Checklist: What to do if you are in a binational couple

1. Check your current situation: where is your common domicile? Do you have a marriage contract or a will?
2. Consult a specialised lawyer: a professional can advise you on the most favourable law and the steps to take (choice of law, change of domicile, etc.).
3. Anticipate potential conflicts: if you feel tension, do not wait for proceedings. International mediation can help reach an agreement on the applicable law.
4. Update your documents: have your civil status documents, contracts, etc., translated and legalised. Keep originals.
5. Act before one of the spouses leaves: once one has left the common domicile, the 'last common domicile' is fixed. If you want French law to apply, ensure that the common life in France is well established before the separation.

Do you find yourself in a similar situation? A first 30-minute consultation with Maître Perucca (€45) can save you months of proceedings — and often much more. Book an appointment →