OTTAWA -- The newest member of the Supreme Court of Canada says he won't hear any cases while a challenge to his appointment is before the courts.

A Toronto lawyer is going to Federal Court in order to test Justice Marc Nadon's eligibility for the highest bench.

Rocco Galati argues that Nadon -- formerly a Federal Court of Appeal judge -- does not qualify to fill one of three slots reserved for judges from Quebec on the top court.

Galati says only judges from Quebec's appeals or superior courts, or lawyers who have belonged to the province's bar for at least 10 years, can be appointed to the Supreme Court.

But former Supreme Court Justice Ian Binnie wrote a legal opinion for the federal government in support of Nadon's appointment.

A spokeswoman for Justice Minister Peter MacKay defended the decision to appoint Nadon.

"Justice Nadon is qualified and we are certain he will serve the court with distinction," Paloma Aguilar wrote in an emailed statement.

"Constitutional experts agree that the Supreme Court Act allows for a sitting Federal Court judge to be appointed to the Supreme Court of Canada -- this includes the opinion of former Supreme Court Justice Ian Binnie."

Nadon's reaction came in a terse, once-sentence news release from the Supreme Court: "Mr. Justice Marc Nadon has decided, in light of the challenge to his appointment pending before the Federal Court, not to participate for the time being in matters before the Supreme Court of Canada."

Galati is asking the court to compel the government to turn over Binnie's legal opinion and any other advice it sought. The Prime Minister's Office has already posted Binnie's opinion on its website.

Galati is also seeking an interim order to stay Nadon's appointment.

NDP Leader Tom Mulcair called the challenge to Nadon's appointment "rather surprising" and "an unusual situation."

Since Galati's complaint "seems to be very substantial," Mulcair said Nadon was right to recuse himself from hearing any cases before the Supreme Court for the time being.

"We're going to follow it very carefully," Mulcair said.

This is the second controversy that has cropped up around Nadon since Prime Minister Stephen Harper tapped him for the court less than two weeks ago.

The first kerfuffle came after he told a parliamentary committee the NHL's Detroit Red Wings drafted him as a youngster.

He later clarified that the team never actually drafted him and that he was using the term in a much looser sense.