The assurance by Minister of State for Foreign Affairs Dubem Onyia represents the government's sharpest statement yet on Islamic court, or Shariah, rulings condemning at least four people to stoning for adultery or rape.
"Nobody will ever be stoned as a result of Shariah law. Nobody," Onyia said.
He spoke at a news conference on Nigeria's preparations for the Miss World pageant, which faces a boycott by a growing number of contestants over the stoning sentence handed a Nigerian woman in March.
An Islamic court in northern Nigeria condemned Amina Lawal, a 31-year-old single mother, for having sex outside marriage. A high court rejected Lawal's appeal in August. She has gone into hiding while awaiting a second appeal by a higher Islamic court.
"There is no way the federal courts can sustain that judgment," Onyia said. He said he spoke as "a member of Cabinet."
Onyia said the government would not force Islamic court systems in a dozen predominantly Muslim northern states to change their laws.
Instead, he said, the cases would be overturned individually in appeals before federal courts.
Onyia and other Nigerian leaders, including President Olusegun Obasanjo, have said the constitution does not allow stonings, amputations, whippings or other common punishments called for under Islamic law.
Nigerian law does allow capital punishment. Onyia did not explain how the government could offer assurances on future rulings by the judicial branch.
Human rights campaigners argued Onyia's pledge was not enough to ensure the safety of Nigerians who have been sentenced to stoning - and others who could be sentenced in the future.
"On the one hand, it is a positive thing that a government minister is saying that death sentences won't be carried out," said Carina Tertsakian of New York-based Human Rights Watch. "But the fact remains that individuals remain sentenced to death in the weeks or months before their cases to make their way through courts. Psychologically, if nothing else, this remains a form of extreme suffering."
Ahmadu Ibrahim, 35, and Fatima Usman, 32, confessed former lovers, also are awaiting an appeal on a ruling by a Shariah court in August sentencing them to death for adultery.
Surimu Mohammed Baranda was condemned to stoning for the alleged rape of a 9-year-old girl. Baranda's family says he is mentally ill and has appealed for clemency.
At least one person has been executed by a Shariah court so far, a man hanged in northern Katsina state in January for stabbing to death a woman and her children.
Another woman sentenced to death by stoning, Safiya Husseini, saw her conviction overthrown by an Islamic court in March.
The sentences have been condemned by international rights groups and some Islamic figures.
The rulings have prompted Panama, Costa Rica, Spain, France, Kenya, Denmark, Belgium, Switzerland and South Africa to boycott the Dec. 7 Miss World contest in Nigeria's capital, Abuja.
Onyia accused Western nations of orchestrating international media coverage of the stoning controversy in an effort to "prevent Nigeria from hosting an important international event."
Some leaders of Nigeria's Muslim community, which represents half of Nigeria's 120 million people, have separately branded the pageant immoral.
By Glenn McKenzie