Washington Revised Code Title 26. Domestic Relations § 26.04.020. Prohibited marriages

(1) Marriages in the following cases are prohibited:

(2) It is unlawful for any person to marry his or her sibling, child, grandchild, aunt, uncle, niece, or nephew.

(3) A marriage between two persons that is recognized as valid in another jurisdiction is valid in this state only if the marriage is not prohibited or made unlawful under subsection (1)(a) or (2) of this section.

(4) A legal union, other than a marriage, between two individuals that was validly formed in another state or jurisdiction and that provides substantially the same rights, benefits, and responsibilities as a marriage, does not prohibit those same two individuals from obtaining a marriage license in Washington.

(5) No state agency or local government may base a decision to penalize, withhold benefits from, license, or refuse to contract with any religious organization based on the opposition to or refusal to provide accommodations, facilities, advantages, privileges, service, or goods related to the solemnization or celebration of a marriage.

(6) No religiously affiliated educational institution shall be required to provide accommodations, facilities, advantages, privileges, service, or goods related to the solemnization or celebration of a marriage, including a use of any campus chapel or church. A religiously affiliated educational institution shall be immune from a civil claim or cause of action, including a claim pursuant to chapter 49.60 RCW, based on its refusal to provide accommodations, facilities, advantages, privileges, service, or goods related to the solemnization or celebration of a marriage under this subsection shall be immune for civil claim or cause of action, including a claim pursuant to chapter 49.60 RCW.