The Jan. 2 decision  overturned a lower court decision limiting rights to two parents. The same-sex partner of the biological mother went to court seeking to be declared a mother of the boy. The ruling is prompting a growing number of pro-marriage groups to call on the federal government to launch more studies on marriage and families.

"It is clear that courts will be asked to fill in many gaps that exist in traditional understandings of family, as a result of changes to the definition of marriage, and parent, in Canadian law," said Catholic Civil Rights League president Phil Horgan in a Jan. 2 news release. "Canadian courts have recognized lesbian parents on birth certificates to the exclusion of any father in the past year. The Court of Appeal has now expanded the number of recognized parents to three in this case. Future cases can be expected to ask to expand that number."

The League intervened in the so-called Three Parents' Case as part of the Alliance for Marriage and Family. The court was told the Ontario boy has three parents, identified as B.B. and C.C., the biological father — a friend of the couple — and mother respectively, and A.A., C.C.'s same-sex partner. The two women would be the primary caregivers for the boy.

The ruling overturned a 2003 decision by Mr. Justice David Aston who ruled he had no jurisdiction over the case.

"This is another unfortunate example of allowing the courts to make decisions in areas where the government should be determining public policy," said Evangelical Fellowship of Canada  general legal counsel Don Hutchinson in a Jan. 2 news release. "There is an old saying that hard cases make bad law. In this instance a difficult and emotionally charged situation has been met with a decision that will have a definite ripple effect throughout our society."

Hutchinson said the case raises not only the question of how many parents each child may now have, but also what determines the number of parents. Is it sexual orientation? Divorce and remarriage? Will the number of parents per child eventually affect the number of spouses allowed in a marriage?

The Catholic Organization for Life and Family (COLF) is another organization calling for further study.

"This court decision should sound an alarm bell for the federal government to do what the French National Assembly did when it called for wide-ranging research on the impact of changing such a fundamental institution as marriage," said COLF director Michele Boulva. "The kind of research we need now in Canada concerns the impact on children of redefining parenthood.... The governments can't let the courts decide these matters."