Is my marriage legal?

It depends on what you believed by you at the time of the ceremony, also what has happened since the ceremony was performed as to property, debts, kids, length of reationship, etc.  Even if the marriage is invalidated, if there have been assets acquired you still may have claims to each other's property.  Give an attorney a call!   

Interesting question.  Okay, here is the statute concerning a marriage ceremony in your state. 

RCW 26.04.060

Marriage before unauthorized cleric -- effect.
A marriage solemnized before any person professing to be a minister or a priest of any religious denomination in this state or professing to be an authorized officer thereof, is not void, nor shall the validity thereof be in any way affected on account of any want of power or authority in such person, if such marriage be consummated with a belief on the part of the persons so married, or either of them, that they have been lawfully joined in marriage.

Did you know it was invalid when you went through the ceremony or did you recently find out? How long have you been married? Do you share joint assets?