After her dismissal, Asma Bougnaoui took her case to the French courts and it was eventually referred to the ECJ.
She was “professionally competent” as a design engineer and sacked solely for refusing to remove her headscarf, its advocate general has advised.
A final ruling will be made by judges, who usually follow legal advice.
Muslims in France have frequently challenged moves by the state and other bodies to regulate religious clothing.
This case reached one of France’s highest courts, the court of cassation, which requested an opinion from the European Court of Justice – whose verdict is binding on member states.
Before Ms Bougnaoui was employed by IT consultancy company Micropole in 2008, she was told in interviews she might not be able to wear the hijab, which covers the head but not the face, at all times.
She provided services to clients on their own premises. But after one such visit, a client complained that her headscarf had “embarrassed” its employees. Micropole asked Ms Bougnaoui to remove her headscarf on her next visit, but she refused and was dismissed on 22 June 2009.
Not ‘legitimate or proportionate’
In her view, ECJ advocate general Eleanor Sharpston said there was “nothing to suggest that Ms Bougnaoui was unable to perform her duties as a design engineer because she wore an Islamic headscarf”. In fact, the company itself had made express reference to her professional competence.
Ms Sharpston rejected the idea that banning workers from wearing religious attire when they came into contact with clients could be necessary “for the protection of individual rights and freedoms necessary for the functioning of a democratic society”.
In conclusion she said Ms Bougnaoui’s dismissal constituted “direct discrimination” and that company policies imposing an entirely neutral dress code could only be justified “if it pursues a legitimate aim and is proportionate”.
The ruling is not binding on the court but advisory. Judges will deliver the final, binding verdict at a later date.