When will an arbitrator's decision be considered unreasonable?

[7] Justice Iacobucci in the decision of Law Society of New Brunswick v. Ryan, 2003 SCC 20, [2003] 1 S.C.R. 247 established when an arbitrator’s decision might be considered unreasonable: 55 A decision will be unreasonable only if there is no line of analysis within the given reasons that could reasonably lead the tribunal from the evidence before it to the conclusion at which it arrived… This means that a decision may satisfy the reasonableness standard if it is supported by a tenable explanation even if this explanation is not one that the reviewing court finds compelling... 56 This does not mean that every element of the reasoning given must independently pass a test for reasonableness. The question is rather whether the reasons, taken as a whole, are tenable as support for the decision. At all times, a court applying a standard of reasonableness must assess the basic adequacy of a reasoned decision remembering that the issue under review does not compel one specific result. Moreover, a reviewing court should not seize on one or more mistakes or elements of the decision which do not affect the decision as a whole.