RCW 46.37.500
Fenders or splash aprons.
</B>(1) Except as authorized under subsection (2) of this section, no person may operate any motor vehicle, trailer, or semitrailer that is not equipped with fenders, covers, flaps, or splash aprons adequate for minimizing the spray or splash of water or mud from the roadway to the rear of the vehicle. All such devices shall be as wide as the tires behind which they are mounted and extend downward at least to the center of the axle.
(2) A motor vehicle that is not less than forty years old or a street rod vehicle that is owned and operated primarily as a collector's item need not be equipped with fenders when the vehicle is used and driven during fair weather on well-maintained, hard-surfaced roads.
RCW 46.16.240
Attachment of plates to vehicles — Violations enumerated.
</B>The vehicle license number plates shall be attached conspicuously at the front and rear of each vehicle for which the same are issued and in such a manner that they can be plainly seen and read at all times. However, if only one license number plate is legally issued for any vehicle such plate shall be conspicuously attached to the rear of such vehicle. Each vehicle license number plate shall be placed or hung in a horizontal position at a distance of not more than four feet from the ground and shall be kept clean so as to be plainly seen and read at all times. In cases where the body construction of the vehicle is such that compliance with this section is impossible, permission to deviate therefrom may be granted by the state patrol. It shall be unlawful to display upon the front or rear of any vehicle, vehicle license number plate or plates other than those furnished by the director for such vehicle or to display upon any vehicle any vehicle license number plate or plates which have been in any manner changed, altered, disfigured or have become illegible. License plate frames may be used on vehicle license number plates only if the frames do not obscure license tabs or identifying letters or numbers on the plates and the plates can be plainly seen and read at all times. It is unlawful to use any holders, frames, or any materials that in any manner change, alter, or make the vehicle license number plates illegible. It shall be unlawful for any person to operate any vehicle unless there shall be displayed thereon valid vehicle license number plates attached as herein provided.
hope this helps, good luck!