A long-standing battle between Canada's largest real estate board and the Competition Bureau over online access to housing market data is headed back to court again this week.

Starting Monday, the Federal Court of Appeal will hear an appeal of a Competition Tribunal ruling that the Toronto Real Estate Board engaged in anti-competitive practices when it restricted how its 45,000 member realtors share home-sales data online.

At the heart of the legal fight is a dispute over what realtors are allowed to do with data from the Multiple Listings Service, an electronic database available only to members of the real estate board that contains details about homes for sale, including past selling prices and realtor commissions.

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Realtors routinely share this information with individual clients, but some in the real estate industry have been fighting to have it available online in bulk through a data feed posted on password-protected websites.

In April, the Competition Tribunal ruled that the real estate board was stifling competition and innovation in the industry by preventing its members in the GTA from creating new online services and tools using home-sales data. The tribunal ordered the real estate board to open up its MLS data for realtors to post online, but that process was put on hold after TREB appealed to the Federal Court.

The real estate board is arguing that sharing home-sales data widely online raises privacy concerns. It wants home owners to be required to give approval before such details are posted online. "Privacy laws obligate TREB and its members to obtain explicit, informed consent from a buyer and a seller to distribute their personal financial information, a right to privacy only they may waive," TREB chief executive officer John DiMichele wrote in August.

The battle over MLS data has dragged on for years. While a Federal Court ruling would apply only to the Toronto Real Estate Board, the case is seen as precedent-setting . The Canadian Real Estate Association, an umbrella group that represents more than 100 real estate boards across the country, has applied to be an intervenor in the case.

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Fraser Beach, a Toronto-area realtor who has been battling TREB over online access to MLS data for nearly a decade, called the Federal Court of Appeal hearing "the final chapter in this quest." Mr. Beach shut down his popular daily newsletter on GTA home sales in September, saying he had received a "cease and desist letter" from the real estate board.

The court is set to hear the case on Monday and Tuesday this week in Toronto.