A tiny island in the Indian Ocean is the latest battleground in France’s immigration debate. High immigration into Mayotte, a French territory where around 80 per cent of people live below the poverty line, is leading to a debate over what it means to be a French citizen. The row may cause France to upend its constitution.

Mayotte, a tiny archipelago measuring 374 square kilometres, has seen its population almost quadruple to around 260,000 since 1991. Around half of the population now comes from the neighbouring Comoros, which voted for independence from France in 1975. Many are attracted by the prospect of their offspring becoming French citizens. But the numbers are now so high that France’s government is considering changing the law for the island.

Removing droit du sol would cause Mayotte to diverge from the rest of the Republic

For years, the droit du sol has conveyed citizenship rights by virtue of a child’s birth on French soil. The acquisition of citizenship is not automatic and is subject to certain conditions, but Gérald Darmanin, France’s interior minister, thinks that those caveats are not enough.

‘It will no longer be possible to become French if you are not yourself the child of a French parent,’ he said during a recent visit to Mayotte, acknowledging that it was a ‘radical decision’. French president Emmanuel Macron, in an interview with L’Humanité, just last week implied that women travelled to the island to give birth to future French citizens.

This debate has already polarised French politics. For the left, this change risks setting France on a slippery slope of watering down the inclusive vales of the French republic. Some, such as Éric Coquerel, a left-wing deputy, are also not convinced that the reform would actually solve the problem of migration from Comores. For those on the right, the mooted changes – which would end droit du sol in Mayotte, reduce family reunification and stop special visas which convey the right to stay in Mayotte but not enter other French regions – do not go far enough. They think that the issue is wider than Mayotte: droit du sol should be abandoned altogether in France.

Removing droit du sol is about more than a dry legal change to a piece of paper: it strikes at the heart of Frenchness. Firebrand left-wing politician Jean Luc Mélanchon summed it up when he said that to be French was to adhere to its revolutionary motto of ‘Liberté, égalité, fraternité,’ regardless of language or religion. For many French people, the concept promotes inclusion by ensuring that all those born on French soil are equal before the law, and ensuring that those born of French parents are not given preferential treatment.

Changing the citizenship laws in Mayotte is not as simple as adopting a new law. Though citizenship laws in Mayotte are subtly different to mainland France, removing droit du sol would cause the territory to diverge from the rest of the Republic. This would violate the constitutional principle of the indivisibility of the French Republic. One of the Republic’s founding principles, it means that there can only be one French people and one law for the whole of France. Changing the constitution to allow a different citizenship law in Mayotte will be no mean feat and the process may further inflame the debate.

It’s true that, compared with America, the French constitution is relatively easy to modify; the French have done just that on 24 occasions since the foundation of the Fifth Republic in 1958. To do so, Macron can either get the support of the country via a referendum, a method which is seldom used, or turn to the Assemblée Nationale and the Sénat, France’s upper house. The latter is controlled largely by the right.

The adoption of a new immigration law last month gives us a flavour of what might be to come if droit du sol is changed. People filled the streets to denounce what they believed to be a ‘racist’ law, with around 75,000 protestors taking to the streets of Paris last month. Debates in the French legislative assembly were similarly polemical. However, more interesting than this, perhaps, was the behaviour of the Sénat, which took advantage of its reading to add a clause removing droit du sol for children not born to French parents. Though the Constitutional Council later removed this clause, citing its incompatibility with the constitution, the concept of droit du sol remains an important point for many on the right, who see it as a key part of the solution to France’s immigration problem.

Right-wing parties are forecast to perform well in the European elections this summer. Macron has nominated right-wing politicians under Gabriel Attal’s new government and adopted an immigration policy which his main rival Marine Le Pen described as an ‘ideological victory’. This apparent pivot looks like an election ploy to hoover up right-wing votes. However, some fear that it will open the door to the far-right if they are in power, by laying the legislative groundwork for them to build on.

France’s droit du sol has historically been seen as a badge of pride by many, as it forges citizens of the Republic regardless of their parents’ origin. Now, as Macron’s government attempts to reform the constitution, it has become a further source of division in French politics.