ST. JOHN'S, N.L. -- The Supreme Court of Canada will be asked Tuesday to reopen a notoriously lopsided 1969 deal that has so far generated more than $27.5 billion for Hydro-Quebec, versus about $2 billion for Newfoundland and Labrador. Lawyer Doug Mitchell will argue the contract for the Churchill Falls hydro station in Labrador should be renegotiated to reflect vastly changed circumstances. He says negotiators almost 50 years ago could not have foreseen how energy markets would completely shift, allowing Hydro-Quebec to buy that power at cheap fixed prices then sell it for huge profits. The resulting disparity has fuelled a bitter feud between the two provinces. "It's a landmark contract in Canadian legal history," Mitchell said in an interview. "It's also an important point in law that many jurisdictions are wrestling with: What do you do if there are unforeseen circumstances that change the equilibrium of the contract? Does the law do nothing or does the law do something? "It's a topical issue in Quebec law and Canadian law more broadly -- and, frankly, around the world." At issue is whether partners in long-term deals are obligated by so-called good faith principles to adjust terms over time. Hydro-Quebec says it helped finance Churchill Falls in exchange for price guarantees that don't expire until 2041. This latest bid to reopen the contract "presupposes the existence of a judicial power to review and amend contracts in the event of changed circumstances," says Hydro-Quebec's submission to the high court. "This right does not exist under Quebec civil law irrespective of whether one uses the term ... good faith, duty to co-operate or abuse of right to describe it." Under the 1969 terms, Hydro-Quebec agreed to buy almost all the energy from the Churchill Falls plant. The deal set a fixed price for that power that would decrease in stages over time. Various aspects of the contract have already been argued before the top court on different legal principles, twice, without success. This most recent challenge started when Churchill Falls (Labrador) Corp. Ltd. -- whose parent company is Crown corporation Nalcor Energy -- went to Quebec Superior Court in 2010. It