Clark County booster seat laws require children to use booster seats until they are at least six years old and 60 pounds. A booster seat is only required in Clark County if a child falls in this category. However, booster seats are important until a child can correctly wear a seatbelt. A seatbelt should cross the child's thighs3. If the child is not of a sufficient size for the seat belt to fit correctly, they should continue to use a booster seat.