MONTPELIER, Vt. (AP) – Vermont’s highest court heard arguments Wednesday in a bistate custody dispute between two estranged civil union partners – a case that could become a landmark in the still-evolving family law surrounding same-sex couples.

Rena Lindevaldsen, a lawyer for the conservative legal group Liberty Counsel, represented Lisa Miller-Jenkins by arguing that the civil union between her and Janet Miller-Jenkins was void because the two women lived in Virginia, which does not recognize same-sex relationships.

The two Virginia residents came to Vermont in 2000 and got a civil union. They returned home, where Lisa was artificially inseminated and gave birth to a baby girl, Isabella, now 3. Later they moved to Vermont, where they lived together a little more than a year before splitting up. Lisa returned to Virginia with Isabella and has sought to deny Janet visitation rights.

Lindevaldsen told the Vermont Supreme Court justices that under Vermont marriage law, “You cannot come to the state of Vermont if you reside in another state and try to evade that state’s marriage laws and enter into a marriage here in Vermont.” The same should go for couples in civil unions, she said, emphasizing that she was seeking equality before the law for her client.

That drew a question from Associate Justice John Dooley III, who noted that the vast majority of civil unions performed in Vermont to date have been of couples visiting Vermont from states where such unions are not allowed.

“If we ruled that way a lot of people would be very surprised” to find out that their civil unions were illegitimate, Dooley said. He asked, “Everybody just overlooked the fact that for all these years out-of-staters couldn’t come to Vermont and have civil unions?”

Jennifer Levi, a lawyer with Gay and Lesbian Advocates and Defenders who was representing Janet, urged the court to uphold the orders of Rutland Family Court Judge William Cohen, who found that Janet had parental rights because the child was born during the civil union.

She argued that Lisa had engaged in “forum-shopping,” when, unhappy with the Vermont judge’s order, she sought a more favorable ruling from a judge in Virginia. That order, which is being appealed to the Virginia Court of Appeals, found that since civil unions have no force of law in Virginia, Janet could not derive any parental rights from her civil union with Lisa.

Lisa, who said in an interview last week that she had abandoned “the homosexual lifestyle” and grown more religious since moving back to Virginia with Isabella, did not attend Wednesday’s hearing.

Janet did attend and read a brief statement after the hearing, declining to take reporters’ questions. “I simply want to say that I sincerely believe it is best for my daughter that both of her parents continue to be an active, loving, responsible part of her life,” she said. “I look forward to a fair and compassionate conclusion to this case.”

During the hearing, Lindevaldsen argued that Janet’s parental rights could not have been established by a biological tie and were not established by Janet formally adopting Isabella. She said the lower court’s finding that parental status was conferred by the civil union was incorrect because the civil union was void.

Levi argued during the hearing and afterward that a federal law barring parents disappointed with a custody ruling in one state from seeking a more favorable ruling in another state should apply to the Miller-Jenkins case.

If the two states remain in conflict, the case may have to be decided by the U.S. Supreme Court, Lindevaldsen said after the hearing. Levi called that premature speculation, saying she hoped the two states’ courts would agree to grant Janet visitation rights.