Why I Wanted to Explore Intensity of Review Across the UK and New Zealand

Jack Trevella shares his experience of the difference in UK vs New Zealand courts on the doctrine of reasonableness.

As an Associate at Sharpe Pritchard (the firm that represented the Wednesbury Corporation in Associated Provincial Picture Houses Ltd v Wednesbury Corp) it is somewhat hard to avoid the doctrine of reasonableness. However, the more experience I gained practising in administrative law in the United Kingdom, the more it struck me as curious to why two closely related common law jurisdictions, the United Kingdom and New Zealand, treat the same foundational concept in such different ways.

In my day‑to‑day practice at Sharpe Pritchard, I often see how decisions of public bodies sit at the intersection of law, policy, democratic accountability, and individual rights. The way the United Kingdom courts scrutinise those decisions in terms of reasonableness or rationality varies depending on the interests affected or, to put it another way, the gravity of their potential consequences. They accept that not every decision warrants the same level of scrutiny. Where the stakes are high, judges are prepared to look more closely at decisions – and will demand more of decision-makers by way of justification. This approach has various labels, but variable review or intensity of review are often used to describe it.

However, variable review has been treated with suspicion, if not scorn, in New Zealand. Although some judges of the High Court have entertained the concept, the appellate courts have not endorsed it and indeed have said that the level of attention a court should bring to its task of determining whether the decision is consistent with the legislation under which it is made should not vary. In essence, Wednesbury review in New Zealand remains in its original, monolithic form. That is, courts will only interfere on reasonableness grounds if  a decision is so unreasonable that no reasonable authority could ever have come to it. This approach is highly deferential and rigid.

I found this difference in approach between the UK and New Zealand courts not only academically interesting, but practically significant. In New Zealand, applicants relying on Wednesbury rarely find success, largely in part because of the way in which the courts treat the concept. However, in the UK, while success on reasonableness or irrationality grounds alone is rare, the courts are at least prepared to accept that some decisions deserve closer scrutiny. Accordingly, and unlike in New Zealand, claims brought on irrationality grounds are not necessarily doomed from the outset.

What I hoped to contribute

My goal in writing the New Zealand Law Journal article was not necessarily to take sides for the sake of it, but to:

• Provide a clear summary of how the UK has developed a sophisticated and principled approach to variable review
• Highlight the richness and nuance of recent UK jurisprudence, including distinctions between process and outcome rationality
• Explore why the New Zealand courts have been more hesitant — and what that means for the future
• Invite debate on whether New Zealand’s administrative law could benefit from embracing a more explicit “culture of justification”; and
• Suggest where reform or clarification might come from next

This is an area where legal doctrine intersects with constitutional norms, democratic expectations, and the practical realities of decision‑making. And it seemed an important moment, particularly given recent appointments to the senior judiciary in New Zealand, to map out where the jurisprudence might travel next.

Why comparative analysis matters for public law

Comparative work can sometimes feel abstract. But I believe this particular comparison has real-world value.

Public law is always evolving. The way courts articulate reasonableness today can affect how ministers, councils, regulators, and tribunals exercise power tomorrow. In the UK, moving towards a more contextual and intensified form of review in appropriate cases has helped solidify a culture where decision-makers must justify their choices more carefully, particularly where they have significant consequences.

New Zealand’s choice (whether to follow, adapt, or diverge) will shape its administrative law for years to come.

Where to read the full article

The full analysis is published as: Jack Trevella, “Intensity of review – a tale of two countries”, New Zealand Law Journal, 23(1), February 2026.

---

For further insight and resources on local government legal issues from Sharpe Pritchard, please visit the SharpeEdge page by clicking on the banner below.

 

 

Visit Sharpe Pritchard's new Building Safety Hub, focusing on The Building Safety Act 2022 and its wide-ranging impact.

This article is for general awareness only and does not constitute legal or professional advice. The law may have changed since this page was first published. If you would like further advice and assistance in relation to any issue raised in this article, please contact us by telephone or email This email address is being protected from spambots. You need JavaScript enabled to view it..