This law is not only meant to protect them, but people riding in the front seat.
Illinois State Police say backseat passengers can be projectiles. Fatalities have been caused to front seat passengers who were hit by rear passengers not wearing seat belts.
While the law is viewed as a safety measure by some, others say it is another unnecessary government mandate.
Beginning January 1, passengers sitting the back seat of vehicle will face a $25 fine if caught without wearing a seatbelt.
Safety is the motivation behind the law. State police say, not only are backseat passengers at risk of being ejected from the car in an accident, but rear passengers without seat belts can be a danger to those in the front seat.
"Backseat passengers can be projectiles. They can be thrown around, and unfortunately if they hit a front passenger, they can kill them," said Illinois State Police Trooper Lorraine Ishida.
That is exactly what happened to Paula Doren's husband. Six years ago, Larry Doren was killed in an accident when he was struck by the passenger in the backseat.
"The passenger in the backseat was thrown forward into the backs of the front seats of the car, pushing the driver and the front seat passenger forward," said Doren.
Doren was instrumental in getting the new law passed. It wasn't easy. There were dozens of lawmakers who voted against it. State Representative Monique D. Davis was one of them.
"Twenty-five bucks if they catch you. I'd rather for the police to catch criminals, catch those who are shooting our babies, catch people who are shooting these guns. Don't catch people in the backseat of a car without a seatbelt on," said Davis.
The new law specifically reads that all rear seat passengers 16 and older be buckled up or risk a ticket. Current law calls for kids ages 8-15 to wear seatbelts, and children under the age of 7 must be in a car or booster seat.
The new law does exempt buses, emergency vehicles and taxicabs.