According to the court's Web site, Chief Justice Gilmar Mendes ruled David Goldman's 9-year-old son must be delivered to him by the boy's Brazilian relatives, as a federal court ordered last week.
The ruling put Goldman one step closer to finally being reunited with his son, Sean. The boy was taken by Goldman's now-deceased ex-wife to her native Brazil in 2004, where he has remained. Goldman has been fighting to get him back from the boy's stepfather.
Goldman's New Jersey-based lawyer, Patricia Apy, said late Tuesday that she believed Mendes' order required that Sean be handed over immediately, but she said Goldman's attorneys had not heard from lawyers for the Brazilian family.
Lawyers on both sides have said there was still a chance for the Brazilian family to appeal to Brazil's highest appeals court, though the chances of success seemed slight.
Goldman, who lives in Tinton Falls, New Jersey, declined to comment until he learned more details about the 50-page ruling.
U.S. Rep. Chris Smith, a New Jersey congressman who traveled to Brazil to offer his support, said Goldman was pleased.
"He was elated, a big smile came to his face, but he said 'I'm not going to let my guard down until it's wheels up," Smith said.
Goldman has seen earlier rulings ordering Sean's return be blocked, and for days his supporters have expressed worries the Brazilian family might try to flee or hide Sean.
Calls to the Brazilian family's lawyer were not immediately returned.
Both the U.S. and Brazilian governments argued that the case clearly fell under the Hague Convention, which seeks to ensure that custody decisions are made by the courts in the country where a child originally lived -- in this case, the United States.
A lawyer specializing in the Hague Convention said Tuesday's decision by Mendes was the only right one to make.
"It would be virtually impossible to reconcile international law with a ruling in favor of the Brazilian family," said Greg Lewen of the Miami-based law firm Fowler White Burnett.
He said that if the Hague Convention were not followed by the chief justice, "the State Department should immediately issue a travel advisory warning parents not to go to Brazil with their children."
Goldman launched his case in U.S. and Brazilian courts after Sean was brought by his mother in 2004 to her home country, where she then divorced Goldman and remarried. She died last year in childbirth, and the boy has lived with his stepfather since.
In an interview with The Associated Press on Sunday, Goldman said he would allow Sean's Brazilian relatives to visit with his son if he won the case. "I will not do to them what they've done to Sean and me," he said.
The case has affected diplomatic ties between Brazil and the U.S., and has been discussed by President Barack Obama and Brazilian President Luiz Inacio Lula da Silva.
Last week, a U.S. senator reacted to the case by blocking renewal of a $2.75 billion trade deal that would remove U.S. tariffs on some Brazilian goods. The hold was lifted after Tuesday's ruling and the U.S. Senate quickly passed the trade measure.
The U.S. State Department pressed for the boy to be returned. But a Brazilian Supreme Court justice on Thursday stayed the lower court decision ordering Sean to be turned over to his father.
Goldman and Brazil's attorney general both filed appeals Friday asking the Supreme Court to overturn the justice's decision to block Sean's return while the court considers hearing direct testimony from the boy. On Tuesday, Mendes ruled the order no longer valid.
The Brazilian family's lawyer, Sergio Tostes, had told the AP that he would like to see a negotiated settlement, saying he wanted to end the damage being done to Sean and to U.S.-Brazil relations.
"We're raising the white flag and saying: 'Let's get together, let's talk. We're the adults, we have responsibilities, so let's start to have a constructive conversation,"' Tostes said.
Goldman, however, was never in a mood to negotiate.
"This isn't about a shared custody -- I'm his dad, I'm his only parent," Goldman said. "This isn't a custody case -- it's an abduction case."