The Michigan Supreme Court broke new ground Monday in a dispute over parental rights, saying a woman can seek custody of her partner’s child who was born before their same-sex relationship ended.

Carrie Pueblo has no biological ties to a boy who was born to Rachel Haas in 2008 but had helped raise him. Pueblo insists they would have been married at that time if same-sex marriage had been legal in Michigan, a status that could have given her a formal role in the child’s life even if the marriage had ended.

Same-sex marriage was declared legal in the U.S. in 2015, after Pueblo and Haas had broken up.

“While the decision in this case likely affects few, it is, nonetheless, important for what it represents,” Justice Megan Cavanagh said in a 5-2 opinion.

“Justice does not depend on family composition; all who petition for recognition of their parental rights are entitled to equal treatment under the law,” Cavanagh wrote.

Pueblo and Haas had raised the boy together after their relationship ended. But by 2017, Pueblo said Haas demanded that she stop having contact with the child.

Pueblo now can return to a Kalamazoo County court and attempt to show that she and Haas would have been married, if possible, when the boy was born through in vitro fertilization.

If a judge agrees, Pueblo then can be evaluated for “custody and parenting time,” the Supreme Court said.

Haas’ attorney had urged the Supreme Court in April to stay on the sidelines and let the Legislature change the law if lawmakers believe it would be appropriate. Justice Brian Zahra agreed with that position in his dissent.

“I am uncomfortable with retroactively recognizing a marriage-equivalent relationship. … Courts will be required to dive into all public and private aspects of a now-defunct relationship to hypothesize whether the couple would have chosen to marry,” said Zahra, who was joined by Justice David Viviano.