A grouping of leftist senators including members of the ruling Socialists, Greens and Communists approved a law banning MON810, a type of GM corn produced by US firm Monsanto, that had already been passed by the lower house of parliament, overcoming opposition from right-wing members.
At the same time, the Council of State rejected a request from corn producers to overturn the ban on MON810.
The council said the applicants from the General Association of Corn Producers (AGPM) had failed to make the case that they faced an urgent economic crisis as a result of the ban, pointing to the fact that only a small portion of French corn is grown with GM seeds.
With Paris having twice put temporary bans on GM crops — in 2011 and 2013 — AGPM said Monday's verdicts were "not a surprise".
The agriculture ministry banned MON810 — the only insect-resistant GM corn allowed to be grown in the European Union — in March.
Its authorization is currently under review by the EU as part of a wider look at the use of GM crops, but member states have the right to ban them regardless of rulings from Brussels.
France is pushing to cut Brussels out of the process entirely, with future GM authorizations taken only at the national level.