As we reported, Halle and Gabriel are embroiled in a court battle over whether Halle should be allowed to move to France with the ex-couple's daughter Nahla. Halle believes the kid will be better protected from aggressive paparazzi in France ... thanks to the country's strict anti-pap laws.

But Gabriel's attorney argued Halle and Nahla would be walking right into the lion's den -- because France is the same country where Princess Diana was killed in a wild paparazzi car chase back in 1997.

Halle's lawyer called several French lawyers -- who testified that French judges will nail any photog who goes after a celeb.

Under French laws, paparazzi can't photograph celebrities who don't want their pictures taken -- even if they're out in public.

Photogs who violate the law can be sued for big bucks, and if they harass the celeb they can be criminally prosecuted.