Yesterday’s decision means Wal-Mart must hand over the documents to Saskatchewan’s labour board, or face criminal sanctions.

“This is very significant,” said Paul Meinema, president of United Food and Commercial Workers’ Local 1400, which is trying to organize two Wal-Mart stores in Saskatchewan.

“The highest court in the land has said to Wal-Mart, ‘You have to obey the rules of our province and our country.’”

Andrew Pelletier, a Wal-Mart spokesman, said the retailer is “disappointed but not surprised.”

“We wanted to have this case heard at the Supreme Court of Canada because we felt there were serious and fundamental democratic principles at stake here,” he said.

Wal-Mart said the request violated its right to privacy, calling the documents “irrelevant” to the labour board’s investigation.

That view was shared by a provincial judge who dismissed the order in July, describing the labour board’s request as a “fishing expedition.”

Saskatchewan’s court of appeal later overturned that decision. Wal-Mart then petitioned the Supreme Court to hear its case.

Yesterday’s ruling is a setback for Wal-Mart, which has been facing a series of public relations disasters in the last year over unionizing efforts at its stores, charges that it pays low wages, alleged sex discrimination, the use of illegal workers and accusations it tried to freeze out local competition.

Earlier this week, H. Lee Scott, Wal-Mart’s chief executive, held an unprecedented two-day media event to answer the retailer’s critics. In January, Wal-Mart took out high-priced ads in major U.S. newspapers to spruce up the retailer’s image.

In Canada, the retailer has been waging a war of attrition with the union over organizing efforts at a dozen outlets across the country.

The fight reached a head in February when Wal-Mart announced the closure of a Quebec store that was unionized several months earlier. The company said the outlet was losing money, a claim union critics deny.

Quebec’s labour board censured Wal-Mart for intimidating employees at another store while a union organizer was arrested in Windsor, Ont., for allegedly punching a Wal-Mart employee.

Organizing efforts in Saskatchewan have been marred by accusations of dirty dealing on the part of Wal-Mart and union leaders, charges the labour board is investigating.

A group of employees stepped into the fray with claims they were bullied by organizers into signing union cards and were paid to sign union cards. At least one person affiliated with the union has admitted paying off two employees. The union said the individual was not part of its organizing team.

Saskatchewan’s labour board is hoping Wal-Mart’s documents, such as the union prevention handbook, will shed light on whether company officials pressured workers into making the accusations.