France's highest court has heard an appeal by the city of Grenoble over a nationwide swimming pool ban on the "burkini" swimsuit.
Authorities in the French city have challenged an administrative court, which banned them from allowing people to wear the burkini.
Grenoble municipal council had sparked nationwide controversy in May by relaxing its rules on the swimwear allowed in public pools.
The Council of State is due to deliver its ruling on the burkini ban "as soon as possible" in the coming days.
The "burkini" is a full-body swimsuit typically worn by some Muslim women to uphold their faith.
Interior Minister Gérald Darmanin has said that Grenoble's swimwear policy was an "unacceptable provocation" that undermined France's core secular values that religion cannot be used to inform decisions or policies.
Since 2016, several local French authorities have attempted to outlaw the wearing of the burkini in public places.
But Grenoble mayor Eric Piolle has argued that people suing public services, such as swimming pools, should be allowed to dress as they please.
France's national government, which invoked a law passed last year to combat "Islamist separatism", has opposed Grenoble's attempts to relax the rules.
Last month, a local court in Grenoble suspended the new policy authorising burkinis, arguing that it "seriously undermined" the neutrality of public services.
Judges said that people should be able to "free themselves from this rule for religious purposes."
French MP Pierre-Yves Bournazel has said "the burkini is not the best promotion of equality between women and men," adding that public swimming pools should be places of "neutrality."
The right and the extreme right of France have also asked for more "supervision" of the burkini in French law.
Far-right leader Marine Le Pen condemned the swimsuit as "clothing of Islamist propaganda", saying her party would ban it "definitively".