The Harper government says it is “genuinely surprised” by the Supreme Court’s decision Friday to block its latest appointment to the top court.

In a 6-1decision, the justices rejected Marc Nadon on the grounds that he does not meet the requirements for an appointee from Quebec.

Quebec appointees to the SCC must either come from the Quebec Superior Court, the Quebec Court of Appeal, or must be a current member of the Quebec bar.

Nadon was appointed from the Federal Court of Appeal.

In a statement, the government said it “will review the details of the decision and our options going forward.”

Before appointing Nadon, the Justice Department sought legal advice from former justices and constitutional scholars, and “none of them saw any merit in the position taken by the Court,” the statement noted.

The statement hailed Nadon as “a distinguished and respected legal mind.”

Nadon, 64, will remain a judge on the Federal Court of Appeal. Friday’s ruling only affects Nadon and future Quebec appointees.

The Court also ruled Friday that the federal government cannot unilaterally change the laws surrounding the essential composition of the Supreme Court.

The essential composition of the top court is protected by the constitution, the court said. Any changes must receive unanimous consent from the provinces and Parliament.

Last December, the federal government amended the Supreme Court Act to allow for the appointment of a judge who is either presently, or has been, a member of the Quebec bar for a minimum of 10 years. Nadon would have been eligible under these new guidelines.

After making the changes, the government referred the issue to the top court for an opinion.

"The narrow question is thus whether he was eligible for appointment because he had previously been a member of the Quebec bar," the judges wrote in the decision released Friday.

"In our view, the answer to this question is no: a current judge of the Federal Court of Appeal is not eligible for appointment."

In its decision, the court chose not to decide on the issue of whether a judge could rejoin the Quebec bar for a day to ensure current membership, and therefore be eligible for the top court.

"We note in passing that the reference questions do not ask whether a judge of the Federal Court or Federal Court of Appeal who was a former advocate of at least 10 years standing at the Quebec bar could rejoin the Quebec bar for a day in order to be eligible for appointment to this Court under Sec. 6," the court said Friday.

"We therefore do not decide this issue."

In an extremely rare move, all six justices of the majority authored the decision. Justice Michael Moldaver was the only dissenting judge, while Justice Marshall Rothstein, who was also appointed by Harper, recused himself from the case without explanation.

Nadon decision has wider implications: expert

Lawyer Sebastien Grammond, who represented two groups of retired Quebec judges in the case, said the judgement makes an important statement as to how the Constitution of Canada can be amended.

The Supreme Court is expected to rule later this year or early next year on the constitutionality of Senate reform and abolition.

"Even though the composition of the court is not in the Constitution itself -- it's just an ordinary statute of Parliament -- it's so important," Grammond told CTV's Power Play on Friday. "It deals with an institution that is crucial to our political system, so that it is protected by the Constitution implicitly."

Grammond said the same argument could be made about the Senate.

"So if you intend to abolish the Senate, then you could come to the conclusion that you would also need the unanimity of the provinces," he said.

Harper named Nadon to the top court last September, but questions about his eligibility were raised immediately. Toronto lawyer Rocco Galati challenged the appointment, and Nadon did not take his seat on the bench.

Seven interveners made presentations to the court in January, including the Quebec and federal governments, as well as constitutional law experts.

NDP justice critic Francoise Boivin said Friday that the court made the right decision.

“I’m very, very satisfied with the Supreme Court decision,” Boisvin told reporters in Ottawa. “At the same time I have to regret that through all that process one year later we’re still without a judge from Quebec.”

Liberal Leader Justin Trudeau said Nadon’s appointment and subsequent rejection by the court “raise serious questions about Mr. Harper’s judgment.

"This is a new, precedent-setting decision, and not one that our country should ever have to face. It is imperative that the Prime Minister is seized with addressing the continued vacancy on our country’s highest court."

The prime minister must now find another nominee to replace Nadon. Justice Louis LeBel will reach mandatory retirement age in November, opening another Quebec spot on the top court. There must always be three judges from Quebec on the court.

The court rejected Section 6 of the Supreme Court Act, the part the federal government changed in the legislation passed last year. Section 6 covers the appointment of the three Quebec justices.

With files from CTV Parliamentary Correspondent Omar Sachedina