The State has no income tax. I think this will be shot down by the end of the year.
If the people determining the legality of this are paid by taxpayers, don’t count on it being shot down. It is the hand that feeds them.
Being a former city and county executive in Washington State, there is no provision in state law that gives cities and counties any authority to implement an income tax, otherwise all the cities and counties would have done this back in the 90’s when the state essentially started keeping 99% of all tax revenues for themselves.