A young Muslim woman is challenging France's full-face veil ban at the European Court of Human Rights, based in the French city of Strasbourg.
The woman argues that the niqab, and the burka body covering, accord with her "religious faith, culture and personal convictions".
She denies being under any pressure from her family to wear them.
A leading French feminist group has urged the ECHR to uphold the ban, arguing that it liberates women.
"The full-face veil, by literally burying the body and the face, constitutes a true deletion of the woman as an individual in public," the head of the International League for Women's Rights, Annie Sugier, said in a letter to the court.
France banned the public wearing of most face coverings in 2011, setting fines for offenders of up to 150 euros (£126; $203).
The country is home to the biggest Muslim minority in Western Europe, accounting for about five million people, or nearly 8% of the population. Most have origins in France's former North African colonies.
In another development, the Paris Appeals Court overturned a high court decision by ruling that a private nursery school had been justified in firing an assistant director who refused to remove her Islamic headscarf at work.
Fatima Afif was sacked from the Baby Loup nursery school, in the Paris suburb of Chanteloup-les-Vignes, five years ago under the nursery's private rules. There is no French legislation regulating headscarves in non-state institutions.
'A symbolic violence'
At Wednesday's hearing in Strasbourg, government lawyer Edwige Belliard argued that the law was democratic and backed by "a strong conviction among the French public".
"Wearing the full veil not only makes it difficult to identify a person, it makes her indistinguishable from other full veil wearers and effectively erases the woman who wears it," she told the court.
Ramby de Mello, a British lawyer representing the unnamed woman, said the law violated his client's religious, free speech and privacy rights and made her feel "like a prisoner in her own country".
The veil was "as much part of her identity as our DNA is of ours", he argued.
According to the ECHR, the woman also contends that the law gives rise to "discrimination based on gender, religion and ethnic origin, to the detriment of women who, like herself, wear the full-face veil".
While she is not named in the document, she is described as being a French national who was born in 1990 and lives in France.
The complaint was brought to the court in April 2011, when the law came into effect.
Ms Sugier, whose organisation was founded by the feminist writer Simone de Beauvoir, said the law was "in no way contrary to freedom and dignity".
Instead, she said, it was aimed at the "liberation" of women because the wearing of veils was "totally incompatible with the very idea of equality".
"How can one not see that to wear the full veil is also a symbolic violence to other women?" she added. "Those who do not wear it feel insulted by this sight reminding them of the enclosures suffered in the past."
Supporters of the law argue that Islam does not stipulate the wearing of a veil.
However, some human rights campaigners have condemned the French law. Amnesty International, for instance, has argued that it violates women's "rights to freedom of expression and religion".
According to France's Le Figaro newspaper, the court's ruling is not expected until the middle of next year.