Wash. Rev. Code § 15.65.130
With respect to marketing agreements, the director shall after publication of his or her final decision, invite all producers and handlers affected thereby to assent or agree to the agreement or amendment set out in such decision. Said marketing agreements or amendments thereto shall be binding upon and only upon persons who have agreed thereto in writing and whose written agreement has been filed with the director: PROVIDED, That the filing of such written agreement by a cooperative association shall be binding upon such cooperative and all of its members, and PROVIDED, FURTHER, That the director shall enter into and put into force a marketing agreement or amendment thereto when and only when he or she shall find in addition to the other findings specified in this chapter that said marketing agreement or any amendment thereto has been assented to by a sufficient number of signatories who handle or produce a sufficient volume of the commodity affected to tend to effectuate the declared policies and purposes of this chapter and to accomplish the purposes and objects of such agreement or amendment thereto and provide sufficient moneys from assessments levied to defray the necessary expenses of formulation, issuance, administration, and enforcement. Such agreement shall be deemed to be issued and put into force and effect when the director shall have so notified all persons who have assented thereto.
RCW 15.65.130