TORONTO - Enforcing the law must at times outweigh the need to protect an anonymous source, Ontario's highest court said Friday as it ordered the National Post to surrender documents at the heart of conflict-of-interest allegations against former prime minister Jean Chretien.

The Ontario Court of Appeal overturned an earlier decision quashing an RCMP search warrant issued against the daily newspaper and reporter Andrew McIntosh, who in 2001 was sent what appeared to be a 1997 loan document from the Business Development Bank of Canada.

The document outlined a $615,000 mortgage to the Grand-Mere Inn, located in Chretien's home riding of St-Maurice, Que.

A footnote in the document said the inn owed Chretien's family company $23,040 in 1997, at the same time Chretien was lobbying the bank president to grant the inn a loan.

The newspaper was never able to confirm the document's legitimacy, and a story based on its contents never appeared.

Police eventually concluded the document was a forgery, and set about obtaining both it and the envelope containing it in order to investigate its origins and ultimately prosecute the alleged forger -- the person who gave it to McIntosh's anonymous source.

In 2004, however, Ontario Superior Court Justice Mary Lou Benotto quashed the search warrant and assistance order on the grounds it would break McIntosh's pledge to protect his source, thereby violating the media's "constitutionally entrenched right'' to gather and disseminate information.

"In this case, the eroding of the ability of the press to perform its role in society cannot be outweighed by the Crown's investigation,'' Benotto ruled.

The three-judge Appeals Court panel disagreed.

"The document and the envelope are not merely pieces of evidence tending to show that a crime has been committed -- they are the very actus reus (guilty act) of the alleged crime,'' they wrote in a 23-page decision.

"Without the document and the envelope and the ability to conduct forensic testing of them there can be no further investigation, no ability to get at the truth.''

Intervenors in the case, including the CBC and the Globe and Mail, had argued that ordering the documents be handed over would result in a chill between reporters and sources and impair the ability of the media to properly do its job.

Peter Jacobsen, who represented the Globe, said while media lawyers had been hoping for a different outcome, the ruling makes it clear there are times when the tables would be turned and the privilege between journalists and confidential sources would win out.

"One of the bright spots is that the court did not go as far as the Crown wanted it to go and say that the law enforcement interests always trump the media's claim to a journalist-confidential source privilege,'' Jacobsen said.

"Secondly, they haven't by any means ruled out the concept of there being a journalist-source privilege. This is a case that turns very much on the facts, and it depends on how you view the facts.''

Jacobsen said the lawyers for the Post are discussing with their clients whether to seek leave to appeal the decision to the Supreme Court of Canada.

"It's all under consideration by the lawyers and their clients, but it wouldn't surprise me,'' he said.

If the allegations of forgery were true, the documents would be the central piece of evidence in an "especially grave and heinous crime,'' the Appeals Court concluded -- "a criminal conspiracy to force a duly elected prime minister from office.''

In such cases, the newspaper's right to protect their anonymous source -- particularly one who might be involved in such a crime -- is trumped by the responsibility of police to enforce the laws of the land, the panel wrote.

"Although, in pursuit of their constitutional right to gather and disseminate the news, journalists are entitled to protect their sources, that entitlement loses much of its force when journalists use it to protect the identity of a potential criminal or to conceal possible evidence of a crime.''

McIntosh and the Post, well aware of the possibility the document was a forgery, never published a story based on the contents of the document, Jacobsen noted.

He also said the alleged forger was not the same person who provided the document to McIntosh, who told court he was confident that his source was convinced the document was legitimate.

"It's that person that McIntosh is trying to protect, because that person has been a regular source,'' Jacobsen said.

"Once you burn him, he or she will not be prepared to come forward and give other reliable information to the media . . . and an awful lot of important news stories see the light of day because of confidential sources.''