RCW 48.18.320: Annulment of liability policies.

No insurance contract insuring against loss or damage through legal liability for the bodily injury or death by accident of any individual, or for damage to the property of any person, shall be retroactively annulled by any agreement between the insurer and insured after the occurrence of any such injury, death, or damage for which the insured may be liable, and any such annulment attempted shall be void.