Most municipalities already required documentation of rabies vaccines in order to license dogs and cats, and dogs/cats/ferrets were required to have rabies vaccines to enter the state. However, the rule in the Washington Administrative Code is new.
Washington State Department of Health's page on Rabies Vaccine Requirements can be found here.
The rule reads, in part:
"WAC 246-100-197 (3) An owner of a dog, cat, or ferret shall have it vaccinated against rabies and revaccinated following veterinary and vaccine manufacturer instructions. This requirement does not apply to animal shelters."