Even aside from RCW 9.94A.440, prosecutors, especially the elected ones, have an unrestricted and unreviewable power to enforce some laws and ignore others. Laws against cruelty to animals, commonly violated by corporations, university research departments and medical schools, are rarely enforced by prosecutors. But prosecutors ferociously and unrelentingly persecute recreational drug users, and even persecute suffering medical patients and their caregivers. See any newspaper for documentation. Law is not some self-executing perfection that drops down out of heaven.
Law is political.
It is made by men, and interpreted and enforced by men, for the benefit of some and the detriment of others. Law is a weapon used by the more powerful the police, prosecutors and politicians against the less powerful, the rest of us. Only by sharing power over the law as widely as possible, and that includes sharing power over the law with trial jurors, can we hope to achieve justice. In California, the state legislature lowered the per se standard from .10 to .08 on January 1, 1990. So it has been 10 years that this lower standard has been in place in the State of California.