RCW 9.41.040
Unlawful possession of firearms — Ownership, possession by certain persons — Restoration of right to possess — Penalties.
(2)(a) A person, whether an adult or juvenile, is guilty of the crime of unlawful possession of a firearm in the second degree, if the person does not qualify under subsection (1) of this section for the crime of unlawful possession of a firearm in the first degree and the person owns, has in his or her possession, or has in his or her control any firearm:
(iii) If the person is under eighteen years of age, except as provided in RCW 9.41.042;
RCW 9.41.240
Possession of pistol by person from eighteen to twenty-one.
Unless an exception under RCW 9.41.042, 9.41.050, or 9.41.060 applies, a person at least eighteen years of age, but less than twenty-one years of age, may possess a pistol only:
(1) In the person's place of abode;
(2) At the person's fixed place of business; or
(3) On real property under his or her control.
RCW 9.41.060
Exceptions to restrictions on carrying firearms.
(9) Any person while carrying a pistol unloaded and in a closed opaque case or secure wrapper; or