PORTLAND – Gay and lesbian civil rights advocates have applauded a Supreme Judicial Court ruling that said a gay woman from Freeport who was “committed” to her ex-partner’s biological child is entitled to full parental rights.

The justices unanimously agreed Tuesday that the woman, identified in court documents only as C.E.W., was a “de facto parent” of the 9-year-old boy.

The court said she had all the rights and responsibilities of motherhood, even though she was no longer involved with the boy’s biological mother.

The court held that “adults who have fully and completely undertaken a permanent, unequivocal, committed and responsible parental role in the child’s life” can in some cases be recognized as legal parents, regardless of their sexual orientation or family relationship.

Their role in raising children can last, the court said, even if the adults’ relationship ends.

The decision puts Maine among a small number of states where courts recognize a bond between an adult and a child that does not result from a biological relationship or legal adoption.

“It’s a very child-centered decision,” said Mary Bonauto of Boston-based Gay & Lesbian Advocates & Defenders. “When you have two parents that can’t agree, courts do what courts always do and make decisions on what is in the best interest of the child.”

Bonauto, who helped argue the case, was lead attorney in cases that led to court rulings in favor of gay marriage in Massachusetts and legalization of civil unions in Vermont.

She said the Maine case also advances the legal status of same-sex couples.

According to the decision, the two women had been living together since 1992 and agreed that C.E.W.’s partner would conceive a child through artificial insemination. The women took each other’s last names and signed a joint parenting agreement. The boy was born in 1994.

In February 1999, the couple separated when the biological mother left their home. They signed a second parenting agreement sharing parental costs and decisions, and agreed that the boy’s primary residence and visitations would be determined by the courts.

In November 2000, the biological mother filed a complaint in Superior Court arguing that C.E.W. should not be considered a parent. She claimed that, under Maine law, an individual who is not related to a child by birth or adoption can never be eligible for parental rights unless the legal parent puts the child in jeopardy.

The Superior Court judge disagreed, and the biological mother appealed.

Justice Jon Levy, writing for a five-member majority of the supreme court, said custody and other decisions should be governed by what is in the best interest of the boy, not his relationship to the other family members.

“The child, now age 9, has bonded with C.E.W. as his parent,” Levy wrote. “The undisputed material facts suggest that the child is both happy and healthy.”

Justices Robert Clifford and Paul Rudman wrote a concurring opinion, saying that a de facto parent can have full rights or limited rights. They said each situation should be determined individually in the lower courts.

Bonauto said the ruling does not give same-sex partners the same rights as married couples, who have full parental rights when they divorce regardless of their commitment to their children. De facto parent status “is not an easy test to meet,” she said.

“At least now, gay and lesbian parents will have some opportunity to show that they have been responsible,” she said. “They can say, ‘I have cared for this child. Even though my relationship is over, my relationship with this child is not over.”