Are double edged knives illegal in Washington state?

Answer 1

Washington law prohibits the possession of a "dagger, dirk, or dangerous knife." Dangerous knives are further defined to include switchblades and gravity knives (butterfly knives), but there is no specific definition of dirks and daggers. Most dictionary definitions describe daggers and dirks as long, thin knives designed for stabbing, but some mention double edges.

Your safest policy is to refrain from carrying knives with double edges. If you want or need to carry a knife, carry a conventional one with only a single sharp edge.