The move was prompted after complaints by some of the south-west city's boulangeries that they were unable to close if other bakeries insisted on working seven days a week as they risked losing business.
An initial order to close once a week in July 2010 has now been upheld by the administrative tribunal of the city.
"A majority of us want to have one day a week when we close to give us a chance to rest without having to worry about competition," said Eric Machado, quoted by Aujourd'hui newspaper.
Other bakers and bakery chains are strongly opposed to the enforced closure.
"We've been opening for seven days a week for two years now," said Claude Polidori, who owns three bakeries in the city. "It's working really well and allowed us to employ an extra person."
"We are for freedom," said Polidori. "That those who want to work can do so while others close if they want to."