Dunsmuir v. New Brunswick, 2008 SCC 9, set out to bring a greater degree of clarity to the law surrounding substantive judicial review than had previously been the case. However, the innovations made in Dunsmuir have not been successful in achieving this objective.That administrative action be "lawful, reasonable, and procedurally fair" is a cardinal gospel principle, stricto sensu. Dunsmuir v. New Brunswick, was in this sense a capstone case in Canadian administrative law, an epochal harbinger. It developed from infancy days of the pre-existing Diceyan formalistic era, underscoring formal trifurcation of powers between the judiciary, legislature and executive, to evolve into the teen-hood of 'pragmatic and functional era'. This focused at contextualized meshing of regulation, policy objectives and practicalities. This graduated into a youthful stage during 2002 to 2008, (affectionately referred to as the dysfunctional period) characterized by weariness and frustration to finally culminate into a mature adulthood, fondly called the categorical approach era. The four-factor approach, not been entirely jettisoned though, was marginalized in favor of a categorical approach. This paper situates Dunsmuir into a historical continuum in Part-I and II to assess the degree of possible clarity afforded to the law surrounding substantive judicial review than had previously been the case. This assesses the impact of standard of review on a range of administrative decisions indicating a perceptible shift from correctness to reasonableness in areas, hitherto not accorded deferential treatment by the Supreme Court. Part III focuses on failure of Supreme Court to apply the reasonableness standard in a consistent and principled fashion, notwithstanding the promise of "principled framework that is more coherent and workable." Part IV, underscores that the "innovations made in Dunsmuir has not been successful in achieving this objective of clarity on law surrounding substantive judicial review than before" and that Court's post-Dunsmuir approach to reasonableness review is both disappointing and confusing. I have argued that this shortcomings can be remedied by articulating a contextual approach on the lines of reasoning in Baker v Canada (Minister of Citizenship and Immigration), contextualizing the values of "justifiability, transparency and intelligibility" through judicial review in a particular administrative context.