Wash. Rev. Code § 36.56.040
If, from the testimony given before the county legislative authority, it appears that the public interest or welfare would be satisfied by the county assuming the rights, powers, functions, and obligations of the metropolitan municipal corporation, the county legislative authority may declare that to be its intent and assume such rights, powers, functions, and obligations by ordinance or resolution, as the case may be, providing that the county shall be vested with every right, power, function, and obligation currently granted to or possessed by the metropolitan municipal corporation pursuant to chapter 35.58 RCW (including *RCW 35.58.273 relating to levy and use of the motor vehicle excise tax) or other provision of state law, including but not limited to, the power and authority to levy a sales and use tax pursuant to chapter 82.14 RCW or other provision of law: PROVIDED, That such ordinance or resolution shall be submitted to the voters of the county for their adoption and ratification or rejection, and if a majority of the persons voting on the proposition residing within the central city shall vote in favor thereof and a majority of the persons voting on the proposition residing in the metropolitan area outside of the central city shall vote in favor thereof, the ordinance or resolution shall be deemed adopted and ratified.
Upon assumption of the rights, powers, functions, and obligations of the metropolitan municipal corporation by the county, the metropolitan council established pursuant to the provisions of RCW 35.58.120 through 35.58.160 shall be abolished, said provisions shall be inapplicable to the county, and the county legislative authority shall thereafter be vested with all rights, powers, duties, and obligations otherwise vested by law in the metropolitan council: PROVIDED, That in any county with a home rule charter such rights, powers, functions, and obligations shall vest in accordance with the executive and legislative responsibilities defined in such charter.
RCW 36.56.040
*Reviser's note:RCW 35.58.273 was repealed by 2002 c 6 s 2.