Washington state constitution
Article XIV
Section 2

When the seat of government shall have been located as herein provided, the location thereof shall not thereafter be changed except by a vote of two-thirds of all the qualified electors of the state voting on that question, at a general election, at which the question of location of the seat of government shall have been submitted by the legislature.

Structure Washington state constitution

Washington state constitution

Article XIV

Section 1

Section 2

Section 3