The Supreme Court of Canada ruled Friday that the RCMP must serve all of New Brunswick in both English and French.
An Acadian group had challenged an attempt by the RMCP to reduce services in French, including in predominantly anglophone areas.
The RCMP, a federal agency, provides provincial police services on contract to New Brunswick -- Canada's only officially bilingual province.
At issue was whether the RCMP was required to uphold New Brunswick language provisions under the Charter of Rights and Freedoms.
The Federal Court of Canada ruled that the RCMP was required to uphold the provisions but the Federal Court of Appeal reversed the decision.
The appeal court said that the province was responsible for language obligations and that the case should have been resolved in provincial court.
But on Friday, in a 9-0 ruling, the SCC restored the Federal Court ruling.
Supreme Court Justice Michel Bastarache, author of Friday's judgment, wrote that the appeal court's ruling "stressed the fact that the RCMP's obligations are contractual and not constitutional."
"I do not think these two types of obligations are mutually exclusive. It is as a result of the agreement that the RCMP, by participating in a function of the New Brunswick government, has constitutional obligations imposed on it under (the New Brunswick-specific section) of the Charter," wrote Bastarache, a New Brunswicker known for defending language rights.
"The RCMP must fulfill that province's obligations when acting on its behalf.''
The eight-year-old case stemmed from a French-speaking woman, Marie-Claire Paulin, who was pulled over for speeding by a Mountie who didn't speak French.
Paulin was pulled over near Woodstock, in a mainly anglophone section of New Brunswick.
Although the ticket was issued in French, Paulin later joined a court challenge initiated by the Societe des acadiens et acadiennes du Nouveau-Brunswick.
The challenge was against a report that recommended the RCMP reduce its French-speaking obligations in the Atlantic region.
The Acadians said any review needed to respect charter protections for French-speaking people in New Brunswick.
The charter specifically states that any resident "has the right to communicate with, and to receive available services from, any office of an institution of the legislature or government of New Brunswick in English or French.''
With files from The Canadian Press
