This would probably be more appropriately posted in the knife laws subforum, but:
If I'm reading the law correctly it looks like a Class B misdemeanor in Oregon and a Gross misdemeanor in Washington. Local laws could vary.
http://www.ebladestore.com/knife-laws-50-states.shtml
Oregon Public Order Offense 166.240 Carrying of concealed weapons. (1) Except as provided in subsection (2) of this section, any person who carries concealed upon the person any knife having a blade that projects or swings into position by force of a spring or by centrifugal force, any dirk, dagger, ice pick, slungshot, metal knuckles, or any similar instrument by the use of which injury could be inflicted upon the person or property of any other person, commits a Class B misdemeanor.
Washington:
RCW 9.41.250
Dangerous weapons — Penalty.
Every person who:
(1) 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;
(2) Furtively carries with intent to conceal any dagger, dirk, pistol, or other dangerous weapon; or
(3) Uses any contrivance or device for suppressing the noise of any firearm,
is guilty of a gross misdemeanor punishable under chapter 9A.20 RCW.