Legal question about Antique vehicles and the seat belt laws

Click It or Ticket Colorado states it is ILLEGAL to be unbuckled in the front seat. The child passenger safety law clearly defines child safety seat and seat belt use from birth through age 15 as follows:

• The law requires infants to ride in a rear-facing child safety seat until they are at least one year old and weigh less than 20 pounds.
• The law requires children ages one to four years old that weigh at least 20 pounds up to 40 pounds to be restrained in a forward-facing or rear-facing child safety seat.
• The law requires that children who weigh over 40 pounds or who are at least four years old be properly restrained in a child booster seat or with a child safety belt-positioning device. Children must ride in booster seats until they are eight years old.
• A child who is at least eight years old must be properly restrained with a safety belt or child restraint system.