Wash. Rev. Code § 80.32.050
Any corporation incorporated or that may hereafter be incorporated under the laws of this state or any state or territory of the United States, for the purpose of manufacturing, transmitting or selling electric power, may lease or purchase and operate (except in cases where such lease or purchase is prohibited by the Constitution of this state) the whole or any part of the plant for manufacturing or distributing electric power or energy of any other corporation, heretofore or hereafter constructed, together with the franchises, powers, immunities and all other property or appurtenances appertaining thereto: PROVIDED, That such lease or purchase has been or shall be consented to by stockholders of record holding at least two-thirds in amount of the capital stock or the lessor or grantor corporation; and all such leases and purchases made or entered into prior to the effective date of chapter 173, Laws of 1903, by consent of stockholders as aforesaid are for all intents and purposes hereby ratified and confirmed, saving, however, any vested rights of private parties.
RCW 80.32.050