The long-drawn-out attempt to return Abacha's embezzled funds to the Nigerian government hit a stumbling block when the late dictator's family contested the Swiss justice department's decision to hand over $498 million.
"The Department of Justice made a ruling last August on the case, but this was contested by Abacha's family and so it went to the Federal Supreme Court," government spokesman Viktor Vavricka said.
The court has now ruled that the majority of the funds - $458 million - were "of clearly criminal origin," the justice department said in a statement.
It added a further $7 million, judged to be of probable criminal origin, had been transferred to a holding account in Nigeria pending further investigations.
Nigerian authorities have accused the inner circle of Abacha, a military strongman who died in 1998 after 5 years in power, of plundering up to $3 billion to stash away in offshore accounts.
Swiss banks had deposits of some $700 million from Nigeria, and have already handed back $200 million. Oil-rich Nigeria, which is struggling with poverty and violent clashes, says it will spend the returned money on development projects. Switzerland has issued an extradition order for Abacha's son Abba Abacha, who was arrested in Germany last December on charges of money laundering, fraud and abuse of administrative charges in connection with the case.