OTTAWA -- Stephen Harper has come almost full circle.

The Conservative prime minister who came to office in 2006 cautioning against the power of the courts suffered a political body blow Friday from the highest court in the land -- a Supreme Court stacked with Harper appointees.

By rejecting Justice Marc Nadon, Harper's sixth and most recent pick for the nine-member bench, the remaining Supremes laid down constitutional markers that could proscribe the government's future plans for Senate reform, electoral changes and the appointment of judges.

Not only was Nadon, a semi-retired Federal Court of Appeal justice, found to not have the proper qualifications laid out in the Supreme Court Act for a Quebec nominee to the top bench, but the government's efforts to rewrite the rules were thwarted.

The government does not have the authority to amend the Act, wrote six of seven judges, saying "the unanimous consent of Parliament and all provincial legislatures is required for amendments to the Constitution relating to the 'composition of the Supreme Court."'

The government appeared to be caught flat-footed by the twin rebukes.

A statement from the Prime Minister's Office said it was "genuinely surprised" and would review its options, all the while stressing Nadon's appointment had been vetted by two former Supreme Court justices and a committee of MPs.

"At no time did any (committee) members, including from the Opposition, object to appointing a member of the Federal Court of Appeal to the Supreme Court," it said -- a claim hotly disputed Friday by one NDP MP on the committee who accused the PMO of "talking through its hat."

As for the government's options, legal scholars were left scratching their heads.

Carissima Mathen, a University of Ottawa law professor and constitutional lawyer who followed the Nadon reference closely, said the government was "pretty cavalier" in how it appointed him.

"Will they accept defeat, or will they look for other ways to get around this?" she wondered. "I think it's really important for public confidence that they actually accept when they have been defeated."

It was the second muscular reminder from the high court in as many days that the Constitution reigns supreme.

On Thursday, a retroactive element in the Conservative tough-on-crime agenda dealing with parole eligibility was struck down, with the court reminding the government that passing unconstitutional laws brings the justice system into disrepute.

Their week's work will have implications for a number of high-profile Conservative government agenda items, notably Senate reform.

"It's quite easy to extrapolate today's decision to the Senate reference," said Sebastien Grammond, a constitutional law expert at the University of Ottawa who also argued the case on behalf of an interveners group that represented provincial court judges.

"I think it would be relevant to the issue of the abolition of the Senate. You can make the argument that it requires unanimity because it has a central importance in our political institutions."

Green party Leader Elizabeth May issued a release that drew the next obvious inference -- a constitutional challenge to the government's deeply controversial "Fair Elections Act" that rewrites the way Canadian elections are conducted and, some argue, tilts the field in the Conservative party's favour.

May urged the government to "stop wasting Parliament's time and stop clogging the courts with legislation that was, on its face, unlikely to survive a court challenge, but which the House keeps passing in blind disregard of the consequences."

Liberal Leader Justin Trudeau said the government has some big decisions ahead, such as Senate reform and assisted suicide.

"These are big deals and the prime minister has failed in one of his fundamental responsibilities," he said. "Now we're going to start over again, and the prime minister will hopefully get the appointment right this time."

Trudeau said the ruling is an affirmation that Canadian federalism works, and it comes "at a convenient time for people who believe in the strength and functioning of Canada."

Others saw little to praise in a messy process that tarred everyone from the government to the court to Nadon himself. The 64-year-old may now be on the hook to repay the hefty Supreme Court salary he's been collecting for five idle months.

Adam Dodek, a constitutional law professor at the University of Ottawa, said the court reference "really blows the lid off the federal government's claim that their way of appointing Supreme Court judges is open and transparent and accountable."

The ruling also resonated on the Quebec election trail, where questions linger about whether the Parti Quebecois would hold another referendum.

"It demonstrates that when Quebec stands up, we can succeed," leader Pauline Marois said of the decision during a campaign stop in Quebec City.

"In this case, there was no other choice: Mr. Harper erred in seeking to appoint Judge Nadon."

Marois also interpreted the ruling as vindication of Quebec's decision to intervene in the case.

"There are people who said ... that it was a bit exaggerated, appearing before the Supreme Court to defend such a point of view," she said. "We defended our point of view. And we won. And I'm very happy."

Rocco Galati, the Toronto lawyer who first challenged the Nadon appointment, welcomed the court's decision, but said it shouldn't have fallen to an ordinary citizen to raise the issue.

"When I started this I was very, very clear and convinced that I was right and that this was as clear as a bell to me," Galati said in an interview from Karachi, Pakistan, where he is travelling.

Galati said he's spent a huge amount of time, energy and his own money "to clean up the mess of the subversive government that doesn't want to respect the Constitution."

"Why should a private citizen have to do that, quite frankly?"

There's also the matter of a Supreme Court that has been short a Quebec justice now for the better part of a year, and an opaque appointment process that clearly has flaws.

The government went to the extraordinary length of getting a legal opinion on Nadon's status last summer, paying retired Supreme Court judge Ian Binnie $7,463.65 to write an opinion that was then approved by another former Supreme, Louise Charron, who was paid $4,325.00 for her efforts and Osgoode Hall professor emeritus Peter Hogg, who earned $1,045.25.

The government's $12,833.90 investment did not pay off.

Nadon was declared ineligible because he came from the Federal Court and did not meet the criteria of either coming from the Quebec Superior Court, the Quebec Court of Appeal, or being a current member of the Quebec bar.