I understand that a private arbitrator's(not one ordered by court) decision is not appealable under WA state law? If so, then how can one go about challenging that part of the law as unconstitutional, seems that even if the decision are not complying with the law, the decision can't be appealed.
Lawsuit / Dispute Attorney
By contract you agreed not to appeal the decision beforehand, right? That means you voluntarily agreed to give up any potential constitutional challenge to the arbitrator decision.
Divorce / Separation Lawyer
You can either ask the arbitrator to reconsider or modify their ruling, or you can file a motion with the court to vacate an arbitration decision. However, if the arbitration was decided using the arbitration rules found in RCW 7.04A, it won’t be decided anew; the judge won’t substitute their judgment for the arbitrator’s.
There is a limited time to file a motion. The grounds and time periods are covered in RCW 7.04A, which you can view online at: http://www.mrsc.org/wa/rcwwac/index_dtSearch.html . Two options are: filing a motion for the arbitrator to modify or correct the award, under 7.04A.200 (within 20 days); or filing a motion with superior court to vacate the award, under 7.04A.230 (within 90 days).
The principal reasons for a court to vacate an arbitration award (in 7.04A.230) are:
(a) The award was procured by corruption, fraud, or other undue means;
(b) There was:
(i) Evident partiality by an arbitrator appointed as a neutral;
(ii) Corruption by an arbitrator; or
(iii) Misconduct by an arbitrator prejudicing the rights of a party to the arbitration proceeding;
(c) An arbitrator refused to postpone the hearing upon showing of sufficient cause for postponement, refused to consider evidence material to the controversy, or otherwise conducted the hearing contrary to RCW 7.04A.150, so as to prejudice substantially the rights of a party to the arbitration proceeding . . . .
This answer assumes that the arbitration is covered by RCW 7.04A. In some cases the parties stipulate about what law applies to the arbitration decision, as well as whether the rules of evidence apply. The specific history of your litigation may affect the conclusion.