It wasn't always illegal to have no front plate

>The law required Connecticut motor vehicles to have a front and a rear license plate until 1980. With the passage of PA 80-466, vehicles were required to have only a rear license plate and the normal registration period was made two years instead of one year. This legislation was enacted primarily for fiscal reasons. It originated in the Appropriations Committee and was referred to no other committees with cognizance over the substantive issues involved in going to a single plate. Going from two license plates to one and going to two-year registrations had been identified for the Appropriations Committee by the Department of Motor Vehicles (DMV) as two of several budget options for cutting costs or raising revenue.
By 1986, the General Assembly had decided to reverse the requirement and go back to two plates for most vehicles. (Fire apparatus; motorcycles; camp trailers; commercial trailers; and vehicles displaying dealer, repairer, junk, or transporter plates were allowed to remain with one plate.) The legislature enacted PA 86-388 to convert back to two plates over a six-year period that began on July 1, 1987. All but the exempted classes of vehicles had to display two plates by July 1, 1993. The DMV commissioner had to issue two plates for all new registrations, beginning July 1, 1987. Two plates had to be issued for all registration renewals beginning July 1, 1991.