On the navy base where I worked knife blade length was limited to 3" but they don't specify fixed or folding. My EDC knife was the Benchmade Hidden Canyon Hunter.
Attached FileOut here in Kitsap I've seen people in grocery stores, starbucks, or walmart carrying a >6" fixed blade knife in a sheath on their belts. I don't know what the law says about them and the patchwork laws were probably designed for that purpose.
By the State Constitution they are protected arms, but since nobody wants to be the test case, it's unsettled for the moment. There was one ruling a few years back where they convicted some guy for concealing a kitchen knife, and he appealed on the grounds that knives were arms under WA Article 1 Section 24. The appeals court disagreed only because it was a kitchen knife, which are not considered weapons and thus not arms. We can read into that that a bowie knife is a weapon, and thus a protected arm, but that will take someone getting arrested and challenging the ruling if it goes bad.