Gabriel Aubrey's lawyer will almost certainly use the publication of topless Kate Middleton photographs in his case to keep his and Halle Berry's daughter in America.
The actress is hoping to move to France with Nahla, four, with her actor fiancé Olivier Martinez.
However her case could be harmed if her model ex uses the new press issue in his argument, according to website TMZ.com.
Halle's legal representative has been trying to convince the judge in her custody battle that their child is better off living in France with her mother because the paparazzi are more respectful of celebrities.
Gabriel was already using the paparazzi chasing Princess Diana to her death in 1997 as a reason she would not benefit from the relocation.
Now Gabriel's lawyers could mention the images taken of the Duchess of Cambridge, which were achieved by an intrusive photographer who apparently used a telephoto lens to capture intimate shots of her on a secluded balcony from more than 1km away.
Halle's lawyer had previously called several French lawyers - who testified that French judges will punish any photo press members who pursue the family.
Under French laws, paparazzi cannot photograph famous people who don't want their pictures taken, even if they're out in public.
Photographers who violate the law can be sued and if they harass the well-known person they can be criminally prosecuted.
- Bang! Showbiz