The U.S. State Department argues that former president of Mexico, Ernesto Zedillo, should be granted immunity from a lawsuit filed in Connecticut over the 1997 massacre of 45 people in a Mexican village. 

Zedillo, who is now an international studies professor at Yale University, had argued that his status as a former national leader gave him immunity from the lawsuit. He has denied the allegations that he bears responsibility for the massacre by paramilitary groups in Acteal, in the southern state of Chiapas.

Lawyers for the plaintiffs said they expect the State Department opinion will prevent the lawsuit from proceeding. They said in a statement that they hope nevertheless to have raised public awareness of "underlying wrongs."

A State Department legal adviser, Harold Hongju Koh, wrote in a letter Friday that Zedillo is entitled to immunity because the lawsuit centers on actions taken in his capacity as president. He noted also that the Mexican government had requested a determination of immunity.

"This complaint is predicated on former President Zedillo's actions as President, not private conduct," Koh wrote.

The U.S. Justice Department submitted the letter to U.S. District Court in Hartford, where a judge will make the final determination. It would have been unusual for the U.S. to reject a former head of state's claim for immunity from a lawsuit involving official acts.

Ten unnamed plaintiffs who say they are survivors of the killings sued Zedillo in September 2011, accusing him of crimes against humanity. They are seeking $50 million in damages.

The massacre on Dec. 22, 1997, was the worst instance of violence during a conflict that began when the Zapatista movement staged a brief armed uprising in early 1994 to demand more rights for Indians in Chiapas. Paramilitaries with alleged government ties attacked Roman Catholic activists who sympathized with the rebels during a prayer meeting in Acteal. The assailants killed 45 people over several hours, including children as young as 2 months old.

After the killings, Zedillo denounced them as criminal and urged government and human rights officials to investigate.

The plaintiffs' lawsuit, however, alleges that Zedillo's administration ended peace talks with the Zapatistas and launched a plan to arm and train local militias to fight against them. It also claims Zedillo was aware of the actions in Acteal, covered them up and broke international human rights laws under the Geneva Conventions as well as a host of other laws.

Zedillo was president of Mexico from 1994 to 2000. His lawyers did not immediately respond to a request for comment.

Based on reporting by the Associated Press.

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