Prince Harry and Meghan Markle filed a lawsuit Thursday in Los Angeles against one or more paparazzi whom they accuse of taking pictures of their son without permission, their lawyer told AFP.
"The couple recently learned that someone is shopping photographs of their 14-month-old son, Archie, falsely claiming to have taken them on a 'recent' public outing 'in Malibu,'" the complaint, filed for invasion of privacy, said.
"But Archie has not been in public, let alone in Malibu, since the family arrived" in California, the lawsuit said, noting that the snapshots were actually taken during "activities in the backyard of the residence, unbeknownst" to the couple.
The complaint, which targets unidentified individuals, is based on a California law that prohibits taking images of anyone in their home, even from outside the property.
"No drones, helicopters or telephoto lenses can take away that right," the couple's lawyer, Michael J Kump, said in a statement to AFP.
"The Duke and Duchess of Sussex are filing this lawsuit to protect their young son's right to privacy... and to uncover and stop those who seek to profit from these illegal actions."
Meghan and Harry quit frontline royal duties earlier this year and now live in Los Angeles, Meghan's hometown.
The complaint accuses the paparazzi of flying helicopters and drones over the couple's home and cutting holes in a security fence in order to obtain photographs.
The duke and duchess say they expect to be followed when they go out in public but state that "certain paparazzi and enablers have crossed a red line."
"The plaintiffs will not allow the tabloids to break the law, especially when it involves intimidation, harassment and the addition of a very real security threat on top of what already exists," the complaint said.
Since stepping back from the royal front lines, Harry and Meghan have waged an increasingly bitter war with the media, particularly the British tabloid press.
Harry, 35, has likened what he said was a "ruthless campaign" against his wife to the treatment of his mother, Diana, princess of Wales.
She was killed in a high-speed car crash in Paris in August 1997, while being pursued by paparazzi photographers.