The Revised Code of Washington 9.41.300 says:
(1) It is Unlawful... to enter... with a Weapon
(b) The areas of any Building used in Court Proceedings..., provided; that such areas do not include the common areas..., or the areas of ingress or egress.
***The information below is straight from the Code.***
In addition, the local legislative authority shall provide either a stationary locked box sufficient in size for pistols and key to a weapon owner for weapon storage, or shall designate an official to receive weapons for safekeeping, during the owner's visit to restricted areas of the building. The locked box or designated official shall be located within the same building used in connection with court proceedings. The local legislative authority shall be liable for any negligence causing damage to or loss of a weapon either placed in a locked box or left with an official during the owner's visit to restricted areas of the building.
The local judicial authority shall designate and clearly mark those areas where weapons are prohibited, and shall post notices at each entrance to the building of the prohibition against weapons in the restricted areas.