Wash. Rev. Code § 15.36.541
Nothing in this chapter shall be construed as affecting or being intended to effect a repeal of chapter 15.130 RCW or RCW 69.40.010 through 69.40.025, or of any of such sections, or of any part or provision of any such sections, and if any section or part of a section in this chapter shall be found to contain, cover or effect any matter, topic or thing which is also contained in, covered in or effected by said sections, or by any of them, or by any part thereof, the prohibitions, mandates, directions, and regulations hereof, and the penalties, powers and duties herein prescribed shall be construed to be additional to those prescribed in such sections and not in substitution therefor. And nothing in this chapter shall be construed to forbid the importation, transportation, manufacture, sale, or possession of any article of food which is not prohibited from interstate commerce by the laws of the United States or rules or regulations lawfully made thereunder, if there be a standard of quality, purity and strength therefor authorized by any law of this state, and such article comply therewith and be not misbranded.
RCW 15.36.541