The Supreme Court of Canada could force Quebec into step with the rest of the country on Friday when it releases an important decision on whether common-law partners have a right to spousal support.

Legal experts say that such a ruling could have repercussions for about 1.2 million Quebec residents – the largest concentration of unmarried couples in the world.

"Every other Canadian jurisdiction has created spousal support obligations between common-law partners, so Quebec sticks out on this one," said Rollie Thompson, a family law professor at Dalhousie University.

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However, the court could go even further, extending to common-law couples the right to a fair division of property acquired during a relationship, as married couples have.

Five provinces and territories have already taken that step. Quebec is among the provinces that have resisted this reform.

Friday's decision involves a billionaire and a former Brazilian model. The couple, who can be identified only as Eric and Lola, met in 1992, when she was 17 and he was 32. They had three children during their seven-year relationship.

Lola, the primary caregiver, asserts that she was unable to work outside the home. She maintained that by refusing her persistent requests that they get married, Eric effectively managed to safeguard his vast fortune.

Lola is seeking a monthly payment of $56,000 for herself, a share of the family estate and a lump-sum payment of $50-million. Her ex-partner has given her a $2.5-million home and money to pay many of her other bills.

Lola currently receives child support of about $460,000 a year.

The Quebec Court of Appeal overturned a lower-court decision that Eric did not have to pay spousal support to his former partner. In doing so, the appellate judges struck down a section of the province's Civil Code. However, they left the property division issue alone.

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Many family law experts maintain the time is ripe for the Supreme Court to overrule a controversial 2002 judgment, Walsh v Bona, that denied property division rights to common-law spouses.

The Walsh decision was predicated on the supposition that common-law couples make a conscious choice to avoid the trappings and obligations of marriage.

"Choice must be paramount," it reasoned. "The decision to marry or not is intensely personal. Many ... individuals in conjugal relationships of some permanence have chosen to avoid marriage and the legal consequences that flow from it."

As wrong as most family law experts believe the Walsh decision was, they do not see it as likely that the Supreme Court will back away from it so quickly.

If the court surprises them by turning away from the Walsh ruling, it would likely cite its 1999 Supreme Court decision in the case of M v H, where the judges extended spousal support benefits to same-sex partners.

Prof. Thompson said it is folly to assume that common-law partners undertake a calculated assessment of their future. "They just leave a toothbrush at the other's place one week and, boom, 10 years later find themselves still not married, with a couple of kids," he said.

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During an oral hearing for the Eric v Lola case, the Women's Legal Education and Action Fund argued that female common-law partners not only tend to earn less during a relationship, they habitually come out on the short end because property is divided unequally.

LEAF lawyers Johanne O'Hanlon and Martha McCarthy asserted that millions of people in common law partnerships also harbour an erroneous belief that spousal and property division rights apply to them.

Women are frequently shocked to discover, after separation, that their failure to marry their former partner is going to leave them with little on which to live, Ms. O'Hanlon and Ms. McCarthy said.