The charge against the 48-year-old, who was not publicly named, did not have anything to do with the September 5, 2012 shooting murders of three members of the al-Hilli family and a French cyclist near the village of Chevaline, the chief prosecutor in the Alpine town of Annecy, Eric Maillaud, stressed in a statement.
Instead the charge -- under French law, a criminal probe that an investigating judge has yet to decide whether to take to trial -- had to do with an arsenal of World War II-era weapons discovered at the homes of the former policeman and his in-laws.
The man was not detained pending the outcome of the criminal investigation into the arms, but was not permitted to leave France, possess weapons or make contact with others connected to the probe, the prosecutor said. If tried and convicted, he risks up to 10 years in prison.
The ex-policeman was arrested Tuesday because of his resemblance to an image of a motorcyclist spotted near the 2012 murders. But he was released Friday after investigating officers determined there was no evidence linking him to the killings.
Saad al-Hilli, a 50-year-old Iraqi-born British tourist, was gunned down along with his 47-year-old wife Iqbal and her 74-year-old mother in a woodland car park in the hills above Lake Annecy.
The couple's two daughters, aged seven and four at the time, survived the attack, but a 45-year-old French cyclist, Sylvain Mollier, was killed after apparently stumbling upon the scene.
French and British police have so far failed to make any tangible progress in the case despite a massive effort involving officers on both sides of the Channel.