OTTAWA - Round Two of an epic legal battle over the right of cigarette makers to promote their products lands in Canada's top court Monday.

The decade-old case pits the country's Big Three tobacco companies against the federal government, six intervening provinces and the Canadian Cancer Society.

"What we're asking for is a minimal window to exercise our constitutionally protected freedom of expression," says Catherine Doyle, spokeswoman for Imperial Tobacco Canada.

The federal government and interveners are expected to tell the Supreme Court of Canada that federal advertising restrictions are clear and justifiable, especially in light of advanced science on the health risks of smoking.

The Canadian Cancer Society calls smoking "a public health disaster on a massive, unprecedented scale, killing 45,000 Canadians annually."

"What's at stake is public health," says society lawyer Rob Cunningham.

Tough laws are needed to ensure young people aren't enticed to light up, and to curb "tough, aggressive marketing by the tobacco industry" that undermines attempts to quit, he said in an interview.

"We know that historically in Canada and other countries, tobacco companies exploit loopholes whenever they're given the opportunity to do so."

Moreover, Canada signed a World Health Organization treaty requiring all-out bans on tobacco advertising and sponsorship wherever constitutionally possible, Cunningham says. The international protocol, signed by 144 countries, took effect in 2005.

Imperial wants to produce "very limited - however competitively important - types of advertising and communications," Doyle said in an interview.

"We're essentially asking that tobacco regulations, which we understand are necessary, be clear, unambiguous and reasonable.

"We're not looking to advertise to kids," or to run so-called lifestyle ads that glamourize smoking, Doyle stressed.

"We know that's not right."

But Imperial, along with JTI-Macdonald Corp. and Rothmans, Benson & Hedges Inc., say the 1997 Tobacco Act is so vague it can be interpreted as being a total advertising ban.

As a result "there's been no brand or informational advertising by Canadian (cigarette) manufacturers in the last 10 years in any kind of publication," Doyle said.

"We want to have clarity on what constitutes legal advertising as allowed in the act."

There's no way to forecast how long it will take the high court to deliver a ruling following the hearing Monday, but judgments usually take several months.

Interveners supporting the Tobacco Act restrictions include Ontario, Quebec, Manitoba, New Brunswick, Saskatchewan and British Columbia.

B.C.'s submissions are unique in that they say federal rules don't go far enough and that a total ban is required. Lawyers for the province are expected to argue that tobacco advertising essentially harms smokers since it urges them to fuel an addiction that clouds their reason.

Parliament first passed a total ban on tobacco advertising in 1988. It was challenged by tobacco giant RJR-MacDonald and struck down by the Supreme Court in 1995. A narrow majority of judges said the federal government failed to convincingly link such a ban to decreased smoking rates, or to show that a partial ban would be less effective than a complete prohibition.

The court suggested that Parliament allow information or brand-preference advertising while outlawing ads that promote smoking as a lifestyle or that are aimed at kids.

The new Tobacco Act of 1997 was swiftly challenged again by the major cigarette makers as unconstitutionally restrictive.

A lower-court judge upheld the act entirely, but the Quebec Court of Appeal ruled in 2005 that it's unfair to bar tobacco companies from exhibiting their company names when they sponsor an event. However, the three judges said specific brand names cannot be used in those cases.

The Canadian Grand Prix was dropped from Formula One's 2004 calendar when Ottawa would not soften anti-tobacco sponsorship rules. It was reinstated when organizers raised $30 million (including $12 million from the federal and Quebec governments) to replace lost ad revenue.

Canada's major tobacco companies have not resumed such sponsorships pending the top-court ruling, Doyle said.

The Canadian Cancer Society says smoking rates have dropped to 18 per cent from 30 per cent in the last 12 years. It credits advertising bans, smoking prohibitions in public places, illustrated warnings required on cigarette packages, education and taxation.

"Although sales have declined tremendously, tobacco companies remain very profitable in Canada," Cunningham says.

An Internet profile of Rothmans, Benson & Hedges Inc. suggests business is good. The company's Canadian plants packaged and shipped more than 11.6 billion cigarettes and equivalents in the year ended March 31, 2005, it says. That's an increase of 1.3 billion from the previous year. Output had jumped over the past two years by more than two billion cigarettes and equivalents - representing an increase of more than 20 per cent.