OTTAWA - The Supreme Court of Canada rules Friday in a case which bears on the right of journalists to shield confidential sources.

The National Post and former Post reporter Andrew McIntosh are asking the court to quash a search warrant issued almost a decade ago as part of what became known as the Shawinigate affair.

At stake is McIntosh's guarantee of confidentiality to a source known only as X, who sent the reporter a key document which was later denounced as a forgery.

In 2000, McIntosh was investigating ties between then-prime minister Jean Chretien and the Grand-Mere Inn, a resort in his home riding. McIntosh reported that Chretien had urged the Business Development Bank of Canada to lend money to the inn.

McIntosh later received an envelope from X which contained what appeared to be a 1997 internal loan document from the bank. It said a $615,000 loan to Grand-Mere had allowed the company to pay off a $23,000 debt to a Chretien family corporation.

The bank called the document a forgery. McIntosh testified that X told him the document had arrived in the mail anonymously and X passed it on, believing it to be genuine.

The RCMP were asked to investigate in 2001. They wanted to test the document and envelope for DNA or fingerprints -- which would likely have identified X.

In July 2002, they obtained a search warrant and an assistance order. The order required the National Post to help find the document, which McIntosh said he had stashed in a safe place not in the newspaper's offices.

The Ontario Court of Justice judge who issued the warrant gave the National Post 30 days to consider its options and the newspaper went to court.

A justice of the Ontario Superior Court quashed the warrant in 2004, saying there was only a remote possibility of finding anything of value on the document or envelope.

The Ontario Court of Appeal disagreed in a 2008 ruling, saying that while a journalist's right to protect sources deserves some recognition, in this case it was being used to shield a potential wrongdoer. The court resurrected the warrant.

The Supreme Court heard the case last May.

The decision could uphold the court of appeal. It could extend protections for confidential sources, or it could tinker with the law.

Now, journalists seeking to protect sources have to meet a four-part test. The key is the fourth part of the test, which requires them to show that the public interest in protecting a source overrides the public interest in a police investigation. The court might switch the onus in this test, forcing the Crown to show that its interests trump the protection of a source.

The case has been the subject of a number of unexplained delays. It took the Mounties a year to get around to asking for the warrant. The case was before the appeal court for four years and it took another year to get before the Supreme Court.