My roommate used to tell me this is why he didn't open carry. He said he didn't want to lose his CPL. I am not familiar with the history of the laws, but according to the RCW, it was effective as of -- 1994 sp.s. c 7 §§ 401-410, 413-416, 418-437, and 439-460.
It may have been possible that prior to the preemption law, there were laws regulating the carry. I am not old enough, so maybe one of the older gentlemen or ladies might be able to tell you. However, this is not the case now. Open carry is your guarded right (with certain restricted areas) and concealed carry requires a permit. It is NOT either or. You can do both.