The government of Argentina annulled a decree on Friday prohibiting the extradition of Argentines suspected of torture or murder in the 1976-83 "Dirty War," a landmark move that could lead to dozens of officers and former junta leaders being tried abroad.
Newly elected President Nestor Kirchner, himself briefly detained during the military dictatorship, signed the order after returning from a state visit to the US.
The move came a day after an Argentine judge rocked the military establishment by ordering the arrest of 45 military officials and one civilian at the request of a Spanish judge who charged them with murders of Spanish citizens during the dictatorship.
The orders, which include several elderly and ill former junta leaders already detained on other rights charges, allows Spanish Judge Baltasar Garzon to request the extraditions. Up to 30,000 leftist opponents died during the Dirty War.
Kirchner came to power in May promising to end a "culture of impunity" that he said stained 20 years of democracy. Since then, legal moves against the military men, who still enjoy some legal protection due to amnesty laws in force, snowballed.
The arrest orders include 1976 coup leader Jorge Videla and Emilio Massera, head of the Naval School of Mechanics, which was known as a torture center. Videla is under arrest on other charges and Massera is incapacitated after a stroke.
Former naval captain Alfredo Astiz, known as the "blond angel of death" for the death squad he ran, was also detained, court officials said. French courts sentenced Astiz in absentia to life imprisonment for the murder of two French nuns.
Courts must still rule on a case-by-case basis whether to extradite officials. Amnesty laws for officials involved in crimes during the dictatorship are in force but lower courts have gradually been striking them down.
The Supreme Court is expected to take up the issue and legal and rights experts say there could be a long road ahead before officials arrive handcuffed at a Spanish airport.
"It's progress on the road to justice, to truth, the end of impunity. But I think there is still a long and winding road ahead in spite of this," said Rosa Roisinblit, a leader of Plaza de Mayo grandmothers, an organization that represents victims families.
A military official shot himself in the mouth in a suicide attempt after learning he was among the suspects ordered to be arrested by judge Rodolfo Canicoba Corral. Naval officer Juan Antonio Azic is in critical condition.
At least 40 other officers, including an elected mayor, were detained by authorities on Friday. One civilian was also detained.
The armed forces, reorganized by Kirchner just after he came to power, have ordered officials to obey the courts.
Garzon's probe stemmed from the deaths or disappearances of several hundred Spaniards during military rule in Argentina. Garzon is famous for his ultimately unsuccessful legal crusade against former Chilean dictator Augusto Pinochet.
A former Argentine naval officer was extradited from Mexico last month to be charged in a Spanish court with acts of terrorism and genocide during the military government.
Kirchner's decision will fortify the image a new president increasingly popular at home for shaking up the military top brass and crusading against judges he accused of corruption.