"Is it true that Illinois just passed a new law that everyone in a car must wear a seat belt even if you are an adult in the back seat? Thank you."
Beverly, there is no state law mandating seat belt use for adults in the back seat. Of course, children under 16 must be seat-belted in or ride in a child passenger safety seat anywhere in the vehicle. In addition, if the driver is under the age of 18, every passenger under the age of 19 must be restrained. This does not apply to adults in the back seat (age 19 or older). It is possible that a municipality could have a local ordinance covering adults in the back seat, but I am not aware of any.