Is an arbitrator's exclusion of all parties from an arbitration hearing an error of law?

As the majority opinion correctly notes, ordinarily errors of fact or law made by an arbitrator are not reviewable and a court may not vacate an award that it disagrees with or believes is erroneous. (Gueyffier v. Ann Summers, Ltd. (2008) 43 Cal.4th 1179, 1184.) While they conclude that here the arbitrator exceeded his authority, in my view the exclusion of all representatives of appellant, other than Rodela, from the arbitration hearing is at most an error of law which does not rise to the level of an act in excess of the power of the arbitrator, and is more likely not an error at all.