Conflicting interpretations of the same statute by an administrative tribunal are unlikely to be reasonable, let alone correct, the Alberta Court of Appeal recently held in Altus Group Limited v Calgary (City), 2015 ABCA 86 [Altus].

Many legal decisions today are made by specialized administrative tribunals rather than courts. The decisions can be reviewed by the courts, whether on appeal or by judicial review, but the courts are increasingly deferring to the tribunal’s expertise by refusing to overturn a decision unless it is unreasonable. It is not enough that a decision is incorrect in law, it must be unreasonably incorrect. This deference to administrative tribunals makes it increasingly important to know what kind of decision will be found not only to be incorrect, but unreasonable.

One test often applied in the statutory interpretation context is whether the tribunal chose one of several reasonable interpretations of a statute. It does not have to choose the interpretation that the court would have chosen; it is enough if it chooses one of several reasonable interpretations. But what if the tribunal chooses one reasonable interpretation one day, and another the next? Are both decisions reasonable since each interpretation was itself reasonable? The Court of Appeal of Alberta has said no, not likely.

In Altus, the Court dismissed an appeal from the decision of a chamber’s judge who had cancelled the decision of a Local Assessment Review Board (“ARB”). The ARB decision held, contrary to a previous decision of the Municipal Government Board (a predecessor of sorts to the ARB), that certain landlords of commercial office space were liable for business tax for leasing parking spaces under a municipal taxation bylaw that applied to a “business in premises”. The chambers judge found it was unreasonable for the ARB to reach the opposite statutory interpretation to prior authority on point.

In upholding the decision of the chamber’s judge, the Court of Appeal noted that, strictly speaking, an administrative tribunal does not have to follow its own decisions—it is not bound by the principles ofstare decisis. Further, where numerous reasonable interpretations of legislation exist, the tribunal may change its policy regarding the interpretation it will adopt. That is the case even where an appellate court has found one particular interpretation to be reasonable.

Nevertheless, previous decisions of the tribunal provide important context to the analysis. After noting the “little direct authority” on point, the Court opined that “it is difficult to conceive of meaningful legislation that would allow diametrically opposed interpretations, both of which are reasonable, not to mention correct.” Both the rule of law, to which consistent rules and decisions are fundamental, and the presumption of legislative coherence reinforce this view. While not creating an independent basis for judicial intervention, a previous administrative decision provides a direct comparison against which to judge the tribunal’s decision. The unlikelihood of contradictory interpretations being reasonable is especially the case when interpreting tax statutes, where consistency is particularly important.