British in France After Brexit: French Nationality by Naturalisation or Marriage — Papers, Delays and How to Challenge a Refusal
Since 1 January 2021, British citizens living in France are third-country nationals. The Withdrawal Agreement protects residence for those who were already settled, and the carte de séjour Accord de retrait (Withdrawal Agreement residence card) secures the right to stay, but it does not give the full range of rights that come with French nationality: the right to vote in all elections, unconditional settlement without renewal, easier mobility inside the European Union, and access to certain public posts. For many British families who have made France their permanent home, the next step is therefore a French passport — either through naturalisation par décret (naturalisation by decree) or through a déclaration à raison du mariage (declaration on grounds of marriage to a French spouse). This guide explains both routes in practical detail, sets out the papers to gather and the delays to expect, and shows exactly what to do when the administration says no: ajournement (postponement), rejet (rejection) or opposition du Gouvernement (Government opposition), followed by the administrative and court challenges that can reverse the outcome.
I. How do you obtain French nationality as a British citizen living in France?
French law offers two main doors to a British adult. The first is naturalisation by decree, a favour granted by the State after a long residence and a check on assimilation (integration into the French community). The second is the declaration through marriage to a French citizen, which is a right when the statutory conditions are met, although the Government can still object on narrow grounds. The two routes share one feature: every French term has a precise legal meaning, and the file must prove each condition with dated documents.
A. Are you eligible for naturalisation by decree after five years of habitual residence?
Naturalisation by decree is governed by a short, clear sentence of the Civil Code: “Hors le cas prévu à l’article 21-14-1 , l’acquisition de la nationalité française par décision de l’autorité publique résulte d’une naturalisation accordée par décret à la demande de l’étranger.” That sentence, in article 21-15 of the Civil Code, carries three practical lessons for a British applicant. First, naturalisation is a decision of the public authority, not an automatic right: even when every box is ticked, the minister assesses whether granting nationality is in the interest of France. Second, the procedure starts only with a formal application, now filed online through the ANEF platform (Administration Numérique pour les Étrangers en France, the digital portal for foreign nationals) with a 255 euro tax stamp. Third, the decree is published only after an investigation run by the préfecture (the local State authority representing the Government) and the Ministry of the Interior.
The residence condition is the first filter. Article 21-17 of the Civil Code provides: “Sous réserve des exceptions prévues aux articles 21-18 , 21-19 et 21-20 , la naturalisation ne peut être accordée qu’à l’étranger justifiant d’une résidence habituelle en France pendant les cinq années qui précèdent le dépôt de la demande.” For a British reader, résidence habituelle (habitual residence) means the real and stable centre of your life: the home where you sleep, the place where your family lives, where your tax residence sits and where your daily activity is based. Short holidays in the United Kingdom do not break the five years, but a long return to Britain, a transfer of the family home, or a period without a valid residence document can. The five years are counted backwards from the filing date, so plan the filing month with care and keep proof for the whole period: Withdrawal Agreement cards, tax notices (avis d’imposition, the yearly income-tax assessment), rent receipts or electricity bills, and employment or pension records.
Several statutory reductions of the five-year period exist but they rarely help a standard British file. Time spent studying in France does not by itself cut the period. The exemptions in article 21-19 of the Civil Code concern, among others, former soldiers of the French army and persons who have rendered exceptional services to France — narrow cases that must be documented with military or ministerial papers. Most British applicants should therefore assume the full five years apply, and should file only when the five-year bundle of proof is complete.
The second filter is assimilation. Article 21-24 of the Civil Code states: “Nul ne peut être naturalisé s’il ne justifie de son assimilation à la communauté française, notamment par une connaissance suffisante, selon sa condition, de la langue, de l’histoire, de la culture et de la société françaises, dont le niveau et les modalités d’évaluation sont fixés par décret en Conseil d’Etat, et des droits et devoirs conférés par la nationalité française ainsi que par l’adhésion aux principes et aux valeurs essentiels de la République.” In practice this breaks into four checks. Language comes first: since the reform applicable from 1 January 2026, the applicant must show a level allowing them at least to understand the essential content of concrete or abstract subjects in a complex text, to communicate spontaneously and to express themselves clearly and in detail on a wide range of subjects. British applicants prove this with an approved language certificate at the required level, and the certificate must still be valid on the day of the entretien d’assimilation (the assimilation interview at the préfecture). History, culture and institutions come second: the interview covers the Revolution, the two world wars, Charles de Gaulle, the symbols of the Republic, the national anthem (La Marseillaise), the motto Liberté, Égalité, Fraternité, the organisation of powers, and everyday civic facts such as the region, the département (the administrative county) and the mayor of the town where you live. Adherence to the values of the Republic comes third: equality between women and men, laïcité (secularism, the French principle separating religion and the State), and respect for the laws. At the end of the check, the applicant signs the charte des droits et devoirs du citoyen français (charter of the rights and duties of the French citizen). The terms of the check are set by regulation, as article 21-25 of the Civil Code recalls: “Les conditions dans lesquelles s’effectuera le contrôle de l’assimilation et de l’état de santé de l’étranger en instance de naturalisation seront fixées par décret.”
The third filter is insertion and good conduct: stable and sufficient income in France (salary, pension, or regular British pension paid into a French account and declared in France), payment of taxes, absence of serious criminal convictions, and no polygamy or fraud. The file therefore includes the last three tax notices, employment contracts or pension statements, the British passport and the Withdrawal Agreement card, birth certificates with sworn translations, proof of address, and the language diploma. Every foreign civil-status document must be recent, legalised or apostilled where required, and translated by a sworn translator (traducteur assermenté, a translator officially listed by a French court of appeal). A missing apostille on a British birth certificate is one of the most common avoidable delays.
Delays are long and must be built into your planning. After the online filing, the préfecture checks completeness, summons you for the assimilation interview, and sends a reasoned opinion to the Ministry. The Ministry then decides: grant by decree, ajournement with a waiting period (often two years), or rejet (outright rejection). Eighteen to thirty months from filing to decree is ordinary. Keep every récépissé (receipt) and renew your residence card in parallel: a naturalisation file never excuses an expired right of residence.
B. Can your marriage to a French spouse give you nationality by declaration?
The marriage route is different in nature: it is a declaration, and when the conditions are met the applicant has a right to nationality, subject only to Government opposition on the narrow grounds of unworthiness or lack of assimilation other than linguistic. The opening sentence of article 21-2 of the Civil Code sets the clock: “L’étranger ou apatride qui contracte mariage avec un conjoint de nationalité française peut, après un délai de quatre ans à compter du mariage, acquérir la nationalité française par déclaration à condition qu’à la date de cette déclaration la communauté de vie tant affective que matérielle n’ait pas cessé entre les époux depuis le mariage et que le conjoint français ait conservé sa nationalité.” Four points deserve close attention from a British spouse.
First, the four-year period becomes five years in two frequent British situations: where the foreign spouse cannot show three years of uninterrupted regular residence in France since the wedding, or where the French spouse was not registered on the consular register of French citizens living abroad during the shared life overseas. Many British-French couples who married in London and lived in the United Kingdom before moving to the Dordogne or Brittany fall into the five-year bracket. Check the consular registration (inscription au registre des Français établis hors de France) early, because a missing registration adds a full year.
Second, a marriage celebrated abroad must have been transcribed onto the French civil registers before the declaration. A wedding at the Chelsea Register Office or in Gretna Green produces a British certificate that must be transcribed through the French consulate that covers the place of marriage. Without transcription, the declaration is not receivable. Order a recent copy of the transcribed act (less than three months old) and, where there were earlier marriages, collect every divorce decree or death certificate proving dissolution.
Third, communauté de vie (shared life, both emotional and material) must have been continuous from the wedding to the declaration date. Living under the same roof, sharing bills, raising children, spending holidays together and supporting each other are the classic proofs: joint tax returns, joint bank statements, the family record book (livret de famille), school certificates for the children, and photographs of family life over several years. The Cour de cassation (the supreme court for civil matters) gives this condition real teeth. In its judgment of 10 February 2021, appeal no. 19-50.027, published in the Bulletin, the First Civil Chamber held: “La situation de bigamie d’un des époux à la date de souscription de la déclaration, qui est exclusive de toute communauté de vie affective, fait obstacle à l’acquisition de la nationalité française par le conjoint étranger.” In plain terms, a bigamous situation at the date of the declaration rules out the emotional shared life the statute requires, however long the couple has lived together and however many children they have. British applicants with a complex marital history should therefore settle every question of prior divorce recognition before filing.
Fourth, language and conduct still matter. The foreign spouse must show sufficient knowledge of French, and must have no serious criminal record. Declarations are received by the administrative authority and a receipt is issued once the file proves receivability, as article 26 of the Civil Code organises for marriage declarations. The Government then has two years from the receipt to object by decree of the Conseil d’État (the highest administrative court acting here as adviser to the Government) for unworthiness or lack of assimilation other than linguistic. Article 21-4 of the Civil Code provides: “Le Gouvernement peut s’opposer par décret en Conseil d’Etat, pour indignité ou défaut d’assimilation, autre que linguistique, à l’acquisition de la nationalité française par le conjoint étranger dans un délai de deux ans à compter de la date du récépissé prévu au deuxième alinéa de l’article 26”, adding that an effective situation of polygamy or a conviction for sexual violence against a minor under fifteen constitutes lack of assimilation. If no opposition comes within two years, or if the declaration is registered, nationality is acquired with retroactive effect to the declaration date — but a later discovery of fraud allows the public prosecutor to contest the registration within two years of discovery.
For British couples, the practical choice between the two routes often turns on timing. A British spouse married for four years with three years of French residence and a transcribed marriage can move faster by declaration than by the five-year naturalisation clock. A British partner in a civil partnership (PACS) cannot use the marriage declaration and must go through naturalisation. Same-sex marriages celebrated in the United Kingdom are recognised for the declaration once transcribed. Where the French spouse has lost French nationality, or where the couple separated even briefly, take advice before filing: an ill-prepared declaration that ends in opposition or in a refusal of registration costs two years.
II. What do you do if the administration says no to your French nationality?
A refusal is not the end of the road, but the remedy depends on the exact label on the decision. Naturalisation produces rejections and postponements by the minister; marriage declarations produce refusals of registration and Government oppositions. Each has its own deadline, its own judge, and its own evidence. Reading the decision letter line by line, noting the date of notification and the stated reasons, is the first legal act — and the one that conditions everything that follows.
A. How do you answer an adjournment, a rejection or a Government opposition?
In naturalisation, the decree of 30 December 1993 (decree no. 93-1362) gives the minister two negative tools: rejection where nationality should not be granted, and postponement (ajournement) imposing a waiting period or conditions such as completing language training, stabilising employment, or clearing tax arrears. The administrative courts describe the framework in settled terms. The Administrative Court of Appeal of Nantes, in its judgment of 13 January 2026, no. 25NT00012, recalls: “il appartient au ministre chargé des naturalisations de porter une appréciation sur l’intérêt d’accorder la nationalité française à l’étranger qui la sollicite.” It adds: “Dans le cadre de cet examen d’opportunité, il peut légalement prendre en compte le degré d’assimilation à la société française du postulant.” The same judgment shows how the check works in practice: the court upheld a rejection where the applicant, despite nearly thirty years in France, could not answer simple questions on history, culture and institutions at the assimilation interview, and it accepted that the interview report proved the gap where the questions were neither vague nor unsuited to the applicant and the officer had not behaved in an intimidating way. British applicants should draw the lesson before the interview, not after: prepare the civic programme seriously, bring coherent answers on the Republic, its symbols and your local life, and remain calm and precise.
Every negative naturalisation decision must be challenged first through the compulsory prior administrative appeal (recours administratif préalable obligatoire, known as RAPO) to the minister within two months of notification. This is not optional: going straight to the administrative court (tribunal administratif, the first-level court for disputes with the administration) without the RAPO makes the court claim inadmissible. The general rule on administrative appeals helps here: article L. 411-2 of the Code governing relations between the public and the administration provides that “Toute décision administrative peut faire l’objet, dans le délai imparti pour l’introduction d’un recours contentieux, d’un recours gracieux ou hiérarchique qui interrompt le cours de ce délai.” In naturalisation the RAPO plays that interrupting role: file it by registered letter with acknowledgment of receipt, attach the missing or corrected evidence (new language certificate, payslips showing stable work, proof of tax compliance, evidence of civic knowledge), and answer each stated reason point by point. Silence of the minister for four months on the RAPO counts as an implicit rejection, which can then go to the court.
In the marriage route, two different blocks must be distinguished. A refusal to register the declaration (for an incomplete file, a missing transcription, or a break in shared life) is contested before the civil courts: the applicant seizes the judicial court (tribunal judiciaire, the ordinary civil court) to have the regularity of the declaration recognised. A Government opposition by decree, taken within the two-year window for unworthiness or non-linguistic lack of assimilation, is contested before the administrative courts, ultimately the Conseil d’État. The evidence differs accordingly. Against a refusal of registration, prove the continuous shared life with dated joint documents spanning the whole period since the wedding, the valid transcription, the French nationality of the spouse on the declaration date, and the language level. Against an opposition, attack the stated facts — for example by showing that the alleged conduct is old, isolated and contradicted by years of family and civic life — and show proportionality. Note the asymmetry the statute builds in: for marriage, lack of assimilation other than linguistic can support opposition, while pure language weakness belongs to the registration stage, not to the opposition stage.
One warning covers both routes. Fraud poisons everything. A false statement on shared life, a hidden marriage or divorce, or a forged certificate can lead to annulment of the registration at the request of the public prosecutor within two years of discovery, and can later support déchéance (stripping of nationality) in the grave cases listed by article 25 of the Civil Code for terrorism, attacks on the fundamental interests of the Nation, or fraud-related offences. Never file a document you cannot stand behind, and correct an honest mistake in writing as soon as you spot it.
B. Which court challenge gives you the best chance of overturning the refusal?
The winning challenge is the one filed before the right judge, inside the deadline, with evidence that meets the exact reason given. Three battle plans cover most British files.
First, the naturalisation rejection for lack of assimilation. The judge reviews only for manifest error of assessment (erreur manifeste d’appréciation), because naturalisation is an opportunity decision. That is a light-touch review, so the file must make the error obvious. Rebuild the interview: request the interview report, list each question and your documented answer, and add independent proof of civic integration — certificates from voluntary work, school involvement, local associations, evidence of French-speaking daily life, and a fresh language diploma at the required level. In the Nantes case cited above, the court listed what was missing — dates of the world wars, meaning of the Revolution, Charles de Gaulle, symbols of the Republic, the anthem, the motto, the population, the region, the département and the mayor — and found no proof that the questions were unfair. A British challenger must therefore show either that the report is inaccurate (contemporaneous notes, witness of the interview where allowed, later test results) or that the overall picture has materially changed since (completed civic training, new diploma, sustained community activity). File the case before the Administrative Court of Nantes, which has national jurisdiction for nationality refusals, within two months of the explicit or implicit rejection of the RAPO, and ask the judge to annul and to order re-examination within a set time.
Second, the naturalisation postponement for lack of professional insertion or tax instability. Postponement is lawful where the minister sets a clear period or condition, commonly two years to stabilise work or demonstrate integration. The challenge here is often negotiation rather than litigation: complete the condition early (permanent contract, twelve months of payslips, tax clearance certificate from the service des impôts des particuliers, the local tax office), then file a fresh, stronger application once the period expires, while keeping the RAPO alive on the first decision to preserve deadlines. Where the postponement rests on a factual error — for example income wrongly counted as foreign when it is taxed in France under the France-United Kingdom double tax treaty — a court claim with the corrected tax notices and the treaty-based calculation can succeed.
Third, the marriage-declaration block. Where registration was refused, the civil judge re-examines the full file: shared life, transcription, dates, language. Build a chronological bundle from the wedding day to the declaration day with no gap longer than a few weeks: joint lease or title deeds, joint tax assessments, joint insurance, birth certificates of children, and correspondence addressed to both spouses at the same address. Where the Government has opposed by decree, move fast before the administrative judge and focus on the opposition grounds, because the two-year opposition window means the decree arrives late in the story and the family has often lived years of shared life since. The 10 February 2021 Cour de cassation ruling is a reminder of the limit: bigamy at the declaration date defeats the claim as a matter of principle, since it rules out emotional shared life. Cases without such a structural bar, based on old minor convictions or on disputed facts about daily life, leave real room for argument.
Across all three plans, three practical rules raise the odds. Calendar every deadline from the acknowledgement of receipt, not from the date on the letter: two months for the RAPO, two months for the court, two years of Government opposition risk for marriage declarations. Keep residence rights separate: renew the Withdrawal Agreement card or other residence permit on time, because a gap in lawful residence weakens a fresh naturalisation file and can complicate travel. And keep certified copies of everything sent on ANEF or by post — the administration loses papers, and the applicant who can re-produce a complete dated bundle wins time.
Conclusion
For a British citizen settled in France after Brexit, French nationality is within reach through two well-marked paths: naturalisation by decree after five years of habitual residence with proven assimilation, or declaration through marriage after four years — five in the common cases of recent arrival or life abroad — with continuous emotional and material shared life and a transcribed marriage. Both routes demand the same discipline: complete civil-status papers with apostilles and sworn translations, three to five years of tax and residence proof, a valid language certificate, and serious preparation for the assimilation interview. When the answer is negative, the remedy is coded in the decision itself: compulsory prior appeal then the Administrative Court of Nantes for naturalisation, the judicial court for a refused marriage registration, and the administrative judge for Government opposition, each within two months. Prepare the file as if you will have to defend it, challenge quickly and precisely when you must, and the French passport becomes the natural seal on a British life rebuilt in France.
Need a quick opinion on your case
British citizen in France considering French nationality? Our firm offers a telephone consultation within 48 hours with a lawyer of the firm to review your residence history, your papers and your best route — naturalisation or marriage declaration — and your chances against a refusal. First telephone consultation: 80 EUR including VAT. Call +33 6 46 60 58 22, or write via our contact page with your residence history, your marriage details and any refusal letter you have received.