The Vatican has invoked diplomatic immunity in refusing to deliver a French court summons to the prefect of the Congregation for the Doctrine of the Faith, Cardinal Luis Francisco Ladaria Ferrer, in a case against a French cardinal.

The Holy See informed the French Ministry of Foreign Affairs in September that it would not notify Cardinal Ladaria of an order to testify before the Lyon court regarding a letter he sent while secretary of the CDF.

A Vatican court ruled that the summons was not valid, since the letter was sent in Ladaria's capacity as a minister of Vatican City State and is protected under international law.

The Spanish cardinal was first called to testify last spring in a case against Cardinal Philippe Barbarin of Lyon and six other officials of the Archdiocese of Lyon, who are being prosecuted for allegedly failing to report accusations of abuse by a priest to the police.

The accused abuser, Fr. Bernard Preynat, was charged with having committed sexual abuse against minors from 1986 to 1991, though prosecutors dropped his case in 2016. Preynat was removed from ministry by Cardinal Barbarin in 2015.

Victims of Preynat are the plaintiffs in the trial, which is scheduled to begin in January 2019, after two postponements after a lack of response from Ladaria. The court decided last month to continue without his testimony.

In Ladaria's letter to the Archbishop of Lyon, which was found in a police search of the archdiocesan offices, he advised Barbarin to take disciplinary action against Preynat, "while avoiding public scandal."

The plaintiffs' lawyers want Ladaria to testify as to whether the direction to prevent scandal was intended as an injunction to avoid going to court, in which case they accuse the CDF prefect of being complicit in failing to report the allegedly abusive priest to authorities.

Cardinal Barbarin has maintained his innocence of the charges brought against him, though he acknowledges the action he took, after learning of abuse allegations in 2007, was "belated."

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