France's highest administrative court has upheld a ban on full-body "burkini" swimsuits in public pools, rejecting an appeal by the city of Grenoble, reports the BBC.
Last month, Grenoble authorised all swimwear, including burkinis, sparking a legal battle with the government.
Burkinis are worn largely by Muslim women as a way of preserving modesty and upholding their faith.
But the court said it could not allow "selective exceptions to the rules to satisfy religious demands".
The dispute went all the way to the Council of State after a local court in Grenoble suspended the ban on the grounds that it seriously undermined the principle of neutrality in public services.
Interior minister Gérald Darmanin also weighed in, describing the policy as an "unacceptable provocation" that was contrary to French secular values.
France has strict laws on which swimming costumes can be worn and the issue of religious expression in public places is divisive.