There have already been two constitutional decisions this year which rather dramatically (and, to be fair, quite forthrightly) demolished important twenty-year-old precedents. It used to be that governments were not required to repay unconstitutionally-collected taxes because such a requirement would cause "fiscal chaos". No longer. And once upon a time "freedom of association" could not disturb the basic contours of statutory labour law. Them days is definitely over.
I give the Court credit for being honest that it was overruling the past decisions. At the same time, this is a bit troubling. Conventionally, a court decision counts as an authority for the future -- not just for lower courts, but for coordinate courts. This is the doctrine of horizontal stare decisis, well-defended by Larry Solum here. What is remarkable is that there is no real attempt by the Court to grapple with this issue. They just give reasons for their decision as if the previous decision had never occurred, or they were dissenting from it for the first time. No consideration was given to the Court's statements about when it will reform the common law, such as this passage from Final Note:
A change in the common law must be necessary to keep the common law in step with the evolution of society (see, e.g., Salituro, at p. 670; Bow Valley, at para. 93), to clarify a legal principle (see Vetrovec, at p. 819), or to resolve an inconsistency (see Jobidon, at p. 733). In addition, the change should be incremental, and its consequences must be capable of assessment.
In the recent case of Robinson, Lamer C.J., for a majority of the Court, relied on five factors to justify the reversal of an earlier decision of the Court in MacAskill v. The King,  S.C.R. 330. These factors were the existence of previous dissenting opinions in this Court, a trend in the provincial appellate courts to depart from the principles adopted in the original decision, criticism of the case or the adoption of a contrary rule in other jurisdictions, doctrinal criticism of the case and its foundations, and inconsistency of the case with other decisions. While they are not prerequisites for a change in the common law, these factors help to identify compelling reasons for reform. On the other hand, courts will not intervene where the proposed change will have complex and far-reaching effects, setting the law on an unknown course whose ramifications cannot be accurately measured
In both cases, there were dissents and lots of critical commentary, and England declined to follow the earlier Supreme Court of Canada ruling on the recovery of unconstitutional taxes. But none of the other factors suggest grounds for change. Both of this year's constitutional reversals are likely to have "complex and far-reaching effects" and the consequences are not in any obvious way capable of assessment. It's hard to see what evolution society has undergone since the late eighties that is relevant to either of them. Nor was there a trend away from the earlier rules in any of the provincial courts. The Health Unions case is going to be immediately disruptive, since it puts in question half a decade of healthcare restructuring in BC.
In the face of real injustice -- as with Brown v. Board of Education -- I think it is legitimate that stare decisis should give way. And no court should feel bound by overbroad obiter statements. But in the end, I think it is stability that we want most from our legal system. Politics and markets are good at change, but they do so best when the legal structure is as solid as it can be.