I cannot cite a specififc law, so take this however you want:
In a meeting at the Seattle PD West Precinct last year this topic came up. The information given at the time from the PD was that it was legal, as long as you are not waving it around in a threatening manner. Police would consider carrying it in your hand, without a scabbard, as waving it around.
In the same discussion, the subject of cane swords came up. These are swords that are hidden in a cane. This is a concealed weapon, though not covered by the CPL because thatonly actuallyapplies tohandguns.