Yeah, except the state constitution doesn't say that. Instead it says [0]:
> All taxes shall be uniform upon the same class of property within the territorial limits of the authority levying the tax and shall be levied and collected for public purposes only. The word "property" as used herein shall mean and include everything, whether tangible or intangible, subject to ownership.
Which was interpreted by the state Supreme Court in 1933 to mean "no income tax" after the voters approved one by 70% [1].
It's acknowledged by proponents of the city income tax that Seattle is doing this knowing it will be challenged in court. They want a test case so they have standing to go back to the state Supreme Court in hopes of overturning that precedent.
Cities can pass conflicting legislation. It takes a court ruling to rule that it is, in fact, conflicting and kill it (and/or a judge to grant an injunction to stop it in the meantime).
San Francisco banned handguns decades ago. That was eventually ruled invalid because of state preemption, but SF had made its Grand Political Statement. CA taxpayers paid the legal costs. Yay.
Generally, taxes can't be challenged until they are actually collected (one famous example: Obamacare).
> All taxes shall be uniform upon the same class of property within the territorial limits of the authority levying the tax and shall be levied and collected for public purposes only. The word "property" as used herein shall mean and include everything, whether tangible or intangible, subject to ownership.
Which was interpreted by the state Supreme Court in 1933 to mean "no income tax" after the voters approved one by 70% [1].
It's acknowledged by proponents of the city income tax that Seattle is doing this knowing it will be challenged in court. They want a test case so they have standing to go back to the state Supreme Court in hopes of overturning that precedent.
0: http://leg.wa.gov/lawsandagencyrules/documents/12-2010-wasta...
1: http://kuow.org/post/strange-short-story-washington-state-s-...