Awalu Yadudu, special adviser on legal matters to military ruler General Sani Abacha, said the nine members of the Movement for the Survival of Ogoni Peoples were found guilty of murder by a legally constituted court.
"Criminal conduct is not subject to international standards but the domestic laws and procedures of the country concerned," he told the News Agency of Nigeria in the capital Abuja.
The nine were hanged Friday, sparking a wave of condemnation across the world. The Commonwealth suspended Nigeria and said it wanted to see concrete evidence of a move to civil rule within two years, otherwise the African country would be expelled from the association, which groups Britain and its former colonies.
Many countries -- including the United States -- recalled their ambassadors from Lagos in protest and British Prime Minister John Major imposed a total ban on arms sales to Nigeria, urging others to follow suit.
Nigeria retaliated Monday, recalling its envoys from abroad, state radio reported. It said the envoys, especially those in the United States, South Africa and the 15 European Union nations, had been ordered to return home immediately.
Also Monday, Nigerian Foreign Minister Tom Ikimi criticized the Commonwealth's suspension move.
"The impact of this decision on Nigeria will be far-reaching. There is no question that the Commonwealth has taken a big gamble," he told a news conference in Auckland.
He accused the Commonwealth, as it ended a summit in New Zealand, of violating its principles on human rights and good government, set out in the 1991 Harare Declaration.
"Suspending Nigeria is not appropriate," Yadudu said. "It has been carried out without due regard for the rule of non-interference in internal affairs of member countries."
The men were executed for the murder last year of four pro-government Ogoni chiefs. Human rights activists said it was a political trial.
Saro-Wiwa had led a campaign for self-determination for the 500,000-strong Ogoni minority and to get compensation from oil firms for environmental damage to their homeland by foreign oil companies since 1954.
Uncertainty has been thrown around Nigeria's much-delayed $4 billion liquefied natural gas project which was about to take off 25 years after its conception.
Anglo-Dutch oil giant Shell, the technical leader of the joint-venture project involving Nigeria and other oil firms, said Sunday the final decision on the project would be taken by the year-end.
This followed Major's disclosure that he would discuss with Shell its involvement in the project Nigeria considers its future economic mainstay.
Shell, which produces half of Nigerian crude oil, the nation's economic lifeblood, is also under fire from Western lobby groups to quit Nigeria or face a boycott of its oil.
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