The implications of the case are significant — there are 1.2 million Quebecers living in common-law relationships.
Lawyers for the Quebec government argued that the province gives couples the right to settle their own affairs.
However, a lawyer for a woman seeking alimony from her former common-law partner — a wealthy Quebec businessman — said it is not fair that common-law couples don't have the same protection as traditionally married people.
Guy Pratte maintained common-law couples are often unaware they will not have the same protection in the event of a separation.
"Can we really say that it is common sense to think that the majority of spouses knowingly waived any protection?" he said.
The case began several years ago when the Quebec businessman argued he shouldn't have to pay alimony to his ex-partner because they had never been married.
In an earlier ruling, a lower court decided that the man — who was given the name Eric — would not have to pay alimony to the woman identified as Lola.
The couple had three children and lived together for seven years.
That court decision was overturned when the Quebec Court of Appeal ruled partly in Lola's favour.
Common-law couples have varying rights depending on where they live in Canada.
In some provinces, they have alimony and property rights.
But despite the fact that one-third of all Quebec couples are unmarried, it remains the only province that does not recognize common-law unions.
Lola was seeking a monthly payment of $56,000 for herself, a share of the family estate and a lump-sum payment of $50 million.
The man did give her a $2.5-million home and money to pay many of her other bills.
She is currently receiving child support of about $460,000 a year.
The couple were given the names Eric and Lola to protect the identities of their children.