* Court to rule if Indian father has right to custody
* Mother gave daughter up for adoption
* Adoptive parents had custody for two years (Adds reaction, color)
U.S. Supreme Court justices appeared conflicted on Tuesday as they debated the delicate question of whether an American Indian father could take custody of his child from a couple who legally adopted her.
The nine-member court has to determine whether the Indian Child Welfare Act, a law passed in 1978 to prevent Indian families from being torn apart by government welfare agencies, allows Dusten Brown custody of his child, even though he had at one point said he would give up his parental rights.
Several justices, including Chief Justice John Roberts, who has two adopted children, appeared sympathetic to the South Carolina couple who adopted the girl, Veronica, who is now three.
But at least two members of the court, Justice Antonin Scalia and Justice Sonia Sotomayor, indicated some support for Brown and others appeared unsure how to proceed. Justice Clarence Thomas, who took custody of a grandnephew in 1997, did not speak during the argument.
Brown, a member of the Cherokee Nation, a federally recognized American Indian tribe, and a soldier at Fort Sill, Oklahoma, invoked the federal law when the child's mother, Christina Maldonado, gave Veronica up for adoption.
The adoptive parents, Matt and Melanie Capobianco, a Boeing technician and developmental psychologist who live in Charleston had custody of Veronica from just after her birth in September 2009. Brown took custody in December 2011 after a South Carolina court ruled in his favor.
The biological and adoptive parents were all in the courtroom on Tuesday, according to Chrissi Nimmo, a lawyer with the Cherokee Nation, which intervened in the case in support of Brown. "I don't think there was any interaction between any of them," she said.
In reviewing the case, the justices struggled openly with how to apply the federal law, which did not appear to have anticipated the type of dispute before the court.
Justice Anthony Kennedy summed up the atmosphere in the courtroom when he noted that custody cases are the "hardest problems for judges."
Some of his colleagues indicated some strong feelings.
When Brown's lawyer, Charles Rothfeld, said his client was excited about the pregnancy, the chief justice seized on the fact that Brown had no involvement with the mother when she was pregnant or giving birth.
"He was excited by it," Roberts said. "He just didn't want to take any responsibility."
Conversely, Scalia signaled that he did not think the federal law could be interpreted in such a way that would allow the American Indian father to lose his parental rights.
"This guy is the father of the child and they are taking the child away even though he wants it," he said. "And that's not the break-up of an Indian family?"
How the case comes out could hinge on whether a majority finds that broad parental rights under the Indian Child Welfare Act can be limited.
Justice Stephen Breyer indicated he thought they should be, citing a worst-case scenario in which a non-Indian rape victim loses custody of a child to an Indian rapist.
"That's obviously something I find disturbing," he said.
The adoptive parents' lawyer, Lisa Blatt, sought to take advantage of that sense of unease in an impassioned closing argument. She said a ruling in favor of the biological father would mean the court is "basically relegating the child to a piece of property with a sign that says: 'Indian, keep off. Do not disturb.'"
Congress enacted the federal law due to what was described in the statute as an "alarmingly high percentage" of Indian families being broken up by child welfare agencies. As a result, many children were placed with non-Indian families.
After the argument, Nimmo said Brown's team was confident the court will end up "affirming Dusten Brown's right to maintain custody and raise his daughter."
The Capobiancos declined to comment on the argument, but said in a statement that they "miss Veronica terribly" and were grateful the Supreme Court agreed to hear the case.
A ruling is due by the end of June.
The case is Adoptive Couple v. Baby Girl, U.S. Supreme Court, No. 12-399