OTTAWA — Stephen Harper’s hopes of a quick fix for the scandal-plagued Senate were blown to pieces Friday by the Supreme Court of Canada.

In a historic, unanimous decision, the top court advised that the prime minister’s proposals to impose term limits on senators and create a “consultative election” process to choose nominees cannot be done by the federal government alone.

Rather, the court said such reforms would require constitutional amendments, approved by at least seven provinces representing 50 per cent of the population — a route fraught with political landmines which Harper had hoped to avoid.

Moreover, the court set the bar even higher for abolishing the Senate, something Harper has threatened to do if his reform agenda is stymied. Getting rid of the chamber altogether would require the unanimous consent of all 10 provinces, the eight justices said.

Harper sought the top court’s advice after a number of provinces strenuously objected to the federal government’s plans to proceed unilaterally with its reform proposals.

The court accepted the argument of most provinces, that the Senate is a key part of the political bargain struck at Confederation and, consequently, can’t easily be tinkered with — no matter how compelling reform or abolition might seem in the wake of the Senate expenses scandal.

“The Senate is one of Canada’s foundational political institutions,” said the ruling, which was attributed to the court as a whole. “It lies at the heart of the agreements that gave birth to the Canadian federation.”

In creating the Senate, the court said the Fathers of Confederation deliberately chose an appointed chamber, which was supposed to be independent, free of partisanship and able to apply “sober second thought” to legislation without blocking the will of the elected House of Commons.

Turning the Senate, directly or indirectly, into an elected chamber “would fundamentally modify the constitutional architecture … and, by extension, would constitute an amendment to the Constitution,” the court said.

“They would weaken the Senate’s role of sober second thought and would give it the democratic legitimacy to systematically block the House of Commons, contrary to its constitutional design.”

The federal government had argued that consultative elections wouldn’t be binding and, since the prime minister would remain free to appoint whomever he pleases, the change was simply a housekeeping matter.

While it acknowledged the prime minister could, in theory, ignore the results of senatorial elections, the court said: “The purpose of the (reform) is clear: to bring about a Senate with a popular mandate. We cannot assume that future prime ministers will defeat this purpose by ignoring the results of costly and hard-fought consultative elections.”

Similarly, the court said imposing a limit on the term of senators, who currently serve until age 75, would also fundamentally change the constitutional architecture, interfering with senators’ independence.

No matter how long the fixed term, a limit would “imply a finite time in office and necessarily offer a lesser degree of protection from the potential consequences of freely speaking one’s mind on the legislative proposals of the House of Commons.”

The court noted that various constitutional amending procedures require Senate approval and any change to those amending formulas requires unanimous provincial consent. Hence, abolishing the Senate would change the amending formulas and, thus, must also require unanimous consent.

“The process of constitutional amendment in a unicameral system would be qualitatively different from the current process. There would be one less player in the process, one less mechanism of review.”

Here’s the document, in full:

Supreme Court on reference by the Governor in Council concerning reform of the Senate Court by Maclean’s Magazine