By the slimmest of majorities — the deciding vote was cast by Chief Justice Beverley McLachlin — the high court said the country's most culturally distinct province does not have to give common-law couples the same rights as married couples.
The complex, detailed ruling issued Friday means the financial aspects of the province's family law regime are constitutional and do not have to be changed — for now.
The ruling very likely marks the start of a new political discussion over the legal definition of marriage, Quebec's justice minister and lawyers for both sides suggest.
Despite the fact that one-third of all Quebec couples are unmarried, the province's Civil Code does not provide equal rights for those in common-law unions.
"We might be at the point where we need a real reflection on the whole of our family laws," said Justice Minister Bertrand St-Arnaud.
"I'm not closing the door on that."
St-Arnaud said he's pleased the Supreme Court respected Quebec's laws.
But he said it might be time to consider updating the provincial legislation, which has not been touched in a generation, amid a skyrocketing number of common-law relationships in the province.
The case involves a woman and her former lover, a prominent Quebec businessman who contends he should not have to pay alimony because they were never legally married.
It's widely known as the Eric and Lola case, because the pair can't be identified under a provincial family law that protects the identity of their three children.
But as lawyers for both parties were quick to acknowledge Friday, the ruling will create broader political ripples beyond the he-said, she-said issues of this case.
"The implication for Quebec society is the ball is now back — or should be back — in the legislator's court," said Lola's lawyer Guy Pratte.
People in common-law unions should consider drafting their own contracts to protect their interests, but Pratte suggests that may not be preferable, or fair.
"Others will presumably think that is not adequate protection for themselves and their family and that they should put pressure on the Quebec legislators to review their regimes," he said.
"Let's not forget that, however, whether or not Quebec is different from other provinces, every other province affords at least a minimum of protection in respect of support for all these couples."
Pierre Bienvenu, Eric's lawyer, said even though his client prevailed, the ruling has opened up a broader political debate.
He said there were always two dimensions to the case: the legal and the socio-political.
"We have today received the answer to the legal issues raised by this debate," Bienvenu said.
"Will it go back in the political arena? Most likely."
Common-law couples have varying rights depending on where they live in Canada, with some provinces giving them alimony and property rights.
The Supreme Court confined its detailed deliberations in this case to Quebec, so it does not appear that the ruling will have immediate ramifications in other provinces.
Justice Louis LeBel, writing for the five-judge majority, said there was no charter violation at play because the current provincial law promotes autonomy.
"The Quebec National Assembly has not favoured one form of union over another," he wrote.
"The legislature has merely defined the legal content of the different forms of conjugal relationships. It has made consent the key to changing the spouses' mutual patrimonial relationship.
"In this way, it has preserved the freedom of those who wish to organize their patrimonial relationships outside the mandatory statutory framework."
Justice Rosalie Abella, disagreed and said the Quebec legal scheme is unconstitutional.
"The National Assembly enacted economic safeguards for spouses in formal unions based on the need to protect them from the economic consequences of their assumed roles," she wrote.
"Since many spouses in de facto couples exhibit the same functional characteristics as those in formal unions, with the same potential for one partner to be left economically vulnerable or disadvantaged when the relationship ends, their exclusion from similar protections perpetuates historic disadvantage against them based on their marital status."
Bienvenu said the case raised difficult issues and no one should be surprised the high court justices themselves were so divided, and expressed such strongly held views.
Pratte said the ruling shifts the onus back to the Quebec legislature, to ensure there are not "two types of families in Quebec; those that are properly protected, including their children, and those that aren't."
Pratte said his client is disappointed that she lost, "but that does not mean the end for those who believe there should be that type of protection."