U.S. Supreme Court justices peppered attorneys with questions this morning in the custody battle over 3-year-old Veronica as the lawyers argued that the court’s decision could have negative impacts on future cases.

Central to the case, Adoptive Couple v. Baby Girl, is the way two sides define a parent under state and federal laws.

The Indian Child Welfare Act, or ICWA, was designed to stem a tide of children leaving American Indian families through adoption and foster care. It helps place such children with other Indian families or strives to keep them with their biological parents.

But attorneys for Matt and Melanie Capobianco, who took Veronica home to James Island shortly after her birth, argued that her biological father shouldn’t have those rights as a parent to block adoption proceedings because he hadn’t expressed interest in the child or supported the mother during the pregnancy.

Dusten Brown, a member of the Cherokee Nation, learned of the adoption four months later and promptly challenged it through ICWA. His attorneys argued that the law gives him the opportunity to halt the adoption because of his biological link to Veronica.

A family court in Charleston eventually ruled in his favor, and Veronica went to live with Brown in late 2011.

During the one-hour hearing this morning, attorney Lisa Blatt of Washington, who argued for the Capobiancos, told the justices that Brown would have lost his rights as a father under state law and that ICWA doesn’t create a new class of parents that otherwise have no rights.

But Justice Sonia Sotomayor promptly took exception to Blatt’s argument.

“I’m not asking about state law,” she said. “I’m asking about federal law.”

Justice Antonin Scalia also fired questions at Blatt and Paul Clement, a Washington attorney representing Veronica’s court-appointed guardian who supports her return to the Capobiancos.

Blatt and Clement have argued that the adoption of Veronica would not break up any pre-existing Indian family because Veronica had not been a part of one. Her mother is Hispanic; her father wasn’t in her life.

But Scalia countered with questions not just about what was, but about what might have been.

“They’re taking the child away from him even though he wants it,” said Scalia, who sided with an American Indian tribe in 1989, the only other time the Supreme Court has heard an ICWA case. “That is not the breakup of an Indian family? ... He’s the father, the other woman’s the mother. That’s the Indian family: the father, the mother and the kid.”

Scalia and Blatt butted heads frequently during the proceeding. He said that the federal policy was clear. But Blatt said Veronica’s case wasn’t one for which ICWA was intended.

The justices asked questions beyond the facts of the case, instead examining hypothetical situations that could present issues depending on how they rule.

Chief Justice John Roberts, himself an adoptive father, remarked at how “a drop of blood can trigger all these extraordinary rights.” Veronica’s ethnic makeup is about 3/256th American Indian.

Both Roberts and Justice Stephen Breyer asked about situations in which a father who has little contact with his child or with the mother during pregnancy invokes ICWA in order to gain custody over a mother’s wishes and the best interests of a child.

A rape victim, for example, could be at risk of losing her child if a father with American Indian blood argues for custody under ICWA.

“The child would be taken and given to the father who has never seen it and probably just got out of prison,” Breyer said. “That’s obviously something I find disturbing, as a person and also as a judge.”

Brown’s attorney, Charles Rothfeld of Washington, scoffed at the theoretical situation, saying that a court would easily rule that placing a child with such a father “could lead to serious physical or emotional damage.”

Deputy U.S. Solicitor General Edwin Kneedler added argument for Brown and the Cherokee Nation.

In rebuttal, Blatt got the final word.

She warned the justices that their opinion, which is expected before the end of June, would have a domino effort on later custody battles involving American Indians.

A decision to uphold the lower courts’ rulings would make mothers “second-class citizens,” she said, and would give most parental rights to “a tribal member (who) impregnates someone who’s African-American or Jewish or Asian Indian” in a New York City apartment.

“You are relegating adopted parents to go to the back of the bus and wait in line if they can adopt,” she said. “And you’re basically relegating the child, the child to a piece of property with a sign that says, ‘Indian, keep off. Do not disturb.’”

During the hearing, Brown often smiled and chuckled with his new wife, Robin, whom he married in June. The Capobiancos were more stoic as they chatted before the hearing began.

After, neither of the families spoke to the gaggle of journalists gathered on the front steps of the courthouse

Asked what he thought of the proceeding, Matt Capobianco said, “I don’t know what to think.”

Reach Andrew Knapp at 937-5414 or twitter.com/offlede.