I did your google search for you.
more responses here:
http://www.google.com/search?q=washington+self+defense+law&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a
Homicide — By other person — When justifiable.
Homicide is also justifiable when committed either:
(1) In the lawful defense of the slayer, or his or her husband, wife, parent, child, brother, or sister, or of any other person in his presence or company, when there is reasonable ground to apprehend a design on the part of the person slain to commit a felony or to do some great personal injury to the slayer or to any such person, and there is imminent danger of such design being accomplished; or
(2) In the actual resistance of an attempt to commit a felony upon the slayer, in his presence, or upon or in a dwelling, or other place of abode, in which he is.
RCW 9.41.270
Weapons apparently capable of producing bodily harm — Unlawful carrying or handling — Penalty — Exceptions.
(1) It shall be unlawful for any person to carry, exhibit, display, or draw any firearm, dagger, sword, knife or other cutting or stabbing instrument, club, or any other weapon apparently capable of producing bodily harm, in a manner, under circumstances, and at a time and place that either manifests an intent to intimidate another or that warrants alarm for the safety of other persons.
(2) Any person violating the provisions of subsection (1) above shall be guilty of a gross misdemeanor. If any person is convicted of a violation of subsection (1) of this section, the person shall lose his or her concealed pistol license, if any. The court shall send notice of the revocation to the department of licensing, and the city, town, or county which issued the license.
(3) Subsection (1) of this section shall not apply to or affect the following:
(a) Any act committed by a person while in his or her place of abode or fixed place of business;
(b) Any person who by virtue of his or her office or public employment is vested by law with a duty to preserve public safety, maintain public order, or to make arrests for offenses, while in the performance of such duty;
(c) Any person acting for the purpose of protecting himself or herself against the use of presently threatened unlawful force by another, or for the purpose of protecting another against the use of such unlawful force by a third person;
RCW 9A.16.020
Use of force — When lawful.
The use, attempt, or offer to use force upon or toward the person of another is not unlawful in the following cases:
(1) Whenever necessarily used by a public officer in the performance of a legal duty, or a person assisting the officer and acting under the officer's direction;
(2) Whenever necessarily used by a person arresting one who has committed a felony and delivering him or her to a public officer competent to receive him or her into custody;
(3) Whenever used by a party about to be injured, or by another lawfully aiding him or her, in preventing or attempting to prevent an offense against his or her person, or a malicious trespass, or other malicious interference with real or personal property lawfully in his or her possession, in case the force is not more than is necessary;
(4) Whenever reasonably used by a person to detain someone who enters or remains unlawfully in a building or on real property lawfully in the possession of such person, so long as such detention is reasonable in duration and manner to investigate the reason for the detained person's presence on the premises, and so long as the premises in question did not reasonably appear to be intended to be open to members of the public;
(5) Whenever used by a carrier of passengers or the carrier's authorized agent or servant, or other person assisting them at their request in expelling from a carriage, railway car, vessel, or other vehicle, a passenger who refuses to obey a lawful and reasonable regulation prescribed for the conduct of passengers, if such vehicle has first been stopped and the force used is not more than is necessary to expel the offender with reasonable regard to the offender's personal safety;
(6) Whenever used by any person to prevent a mentally ill, mentally incompetent, or mentally disabled person from committing an act dangerous to any person, or in enforcing necessary restraint for the protection or restoration to health of the person, during such period only as is necessary to obtain legal authority for the restraint or custody of the person.
RCW 9.41.250
Dangerous weapons — Penalty — Exemption for law enforcement officers.
(1) Every person who:
(a) Manufactures, sells, or disposes of or possesses any instrument or weapon of the kind usually known as slung shot, sand club, or metal knuckles, or spring blade knife, or any knife the blade of which is automatically released by a spring mechanism or other mechanical device, or any knife having a blade which opens, or falls, or is ejected into position by the force of gravity, or by an outward, downward, or centrifugal thrust or movement;
(b) Furtively carries with intent to conceal any dagger, dirk, pistol, or other dangerous weapon; or
(c) Uses any contrivance or device for suppressing the noise of any firearm,
is guilty of a gross misdemeanor punishable under chapter 9A.20 RCW.
(2) Subsection (1)(a) of this section does not apply to:
(a) The possession of a spring blade knife by a law enforcement officer while the officer:
(i) Is on official duty; or
(ii) Is transporting the knife to or from the place where the knife is stored when the officer is not on official duty; or
(b) The storage of a spring blade knife by a law enforcement officer.