The ruling by the Council of State Friday specifically concerns a ban in the Riviera town of Villeneuve-Loubet, but the binding decision is expected to set a legal precedent for all the 30 or so French resort municipalities that have issued similar decrees.
Lawyers for two human rights groups challenged the legality of the ban to the top court, saying the orders infringe basic freedoms and that mayors have overstepped their powers by telling women what to wear on beaches.
Mayors had cited concern about public order after deadly Islamic extremist attacks this summer, and many officials have argued that burkinis oppress women.
Lawyer Patrice Spinosi, representing the Human Rights League, told reporters that the decision should set a precedent, and that other mayors should conform to it. He also said women who have already received fines can protest them based on Friday’s decision.