Los Angeles police have already ruled out bringing charges over the pictures, taken by a paparazzi photographer.
"Unless a deputy saw the violation, there's nothing we can do," said deputy Luis Castro reports BBC news
"We don't even know if this took place in our jurisdiction."
Spears has defended her actions, saying she was carrying her son Sean in the front seat while she was driving only after feeling threatened by photographers.
"I instinctively took measures to get my baby and me out of harm's way, but the paparazzi continued to stalk us," she said.
It is thought her bodyguard was sitting next to her in the passenger seat at the time.
She called the incident with photographers as a "horrifying, frightful encounter".
"I love my child and would do anything to protect him," she added.
The agency which took the photos denied it had acted inappropriately in getting the shots. Meanwhile , TMZ is reporting that the Toxic singer has had car seats on the brain. On January 15th the singer bought a car seat at Toys 'R Us in Porter Ranch, California, a Los Angeles suburb.
An employee of the store told TMZ Spears came in with her assistant and bought a car seat for her baby, as well as a stroller. The Toys 'R Us manager then installed the car seat in the assistant's car.
Video of Britney Spears leaving a Toys 'R Us with her baby shows the pop star closing the door with the baby on her lap.