French Interior Ministry's local office closed the mosque in Pessac district near the city of Bordeaux for six months on March 14.
France's highest administrative court has dismissed an appeal from the French Interior Ministry that aimed to close a mosque in the southwestern town of Pessac for six months.
The Conseil d'Etat rejected on Tuesday the appeal, deeming the closure "a serious and patently illegal violation of the freedom of worship".
The local interior ministry's office first closed the mosque for six months on March 14 on the grounds that "it promoted radical Islam, incited hatred and justified terrorism".
A local administrative court suspended the closure 10 days later, a decision the government appealed.
It is the first time the court has not upheld a government's decision to close a mosque on the basis of a "white memo", a document composed by French intelligence services, bending the latest trend of mosques' being closed by authorities using an array of powers that rights groups and lawyers say infringe on democratic freedoms.
Among the initial accusations against the Pessac mosque was the sharing of pro-Palestinian views on social media, which the government said were "anti-Semitic", or messages of support to personalities and organisations "promoting a radical Islam".
'Cooling down sign'
But the mosque's lawyer, Sefen Guez Guez, said nothing in the case established a link between the mosque's activities and inciting terrorism.
He said the Pessac mosque was an open and peaceful place of worship, whose members mobilised to defend successfully by gathering in front of the courts during both hearings.
"That decision sets a legal precedent which will slow down the successive mosque closures we've seen these past few months, Guez Guez said.
"We hope it is a cooling down sign."
The Interior Ministry said it duly noted the decision and declined to comment further.