The country has just passed the 20th anniversary of a key component of our constitution.

The New Zealand Bill of Rights Act came into effect in 1990. To understand its value, we need to understand what it does.

It affirms the existence of a number of fundamental rights, none of which are controversial.

You have a right to life and a right not to be subjected to degrading treatment.

These are rights enjoyed by all, including by the victims of crime.

There are various rights that are essential for a participatory democracy, from the right to vote to the right to freedom of association or freedom of expression which extends to the corporations that produce most of our media.

There are rights not to be discriminated against and rights to cultural identity.

These rights are clearly key components of what makes Aotearoa a place that ranks among the best countries to come to.

And there are minimum rights to ensure that criminal trials are fair. Even in this apparent age of popular punitiveness, all but a very few would accept that a criminal justice system doesn't count for much if it does not achieve justice.

These rights were developed over centuries as common standards appropriate for a civilised society.

They were the subject of lengthy discussion within the United Nations before being formulated in the International Covenant on Civil and Political Rights 1966, to which New Zealand is a party.

And so they are rights enjoyed by all residents of New Zealand in international law.

The first thing the NZ Bill of Rights Act does is to affirm that these rights exist in law and can be raised in the courts here.

The real genius of the act is how it incorporates those rights while preserving the central role of Parliament to pass laws.

It makes clear that a statute that is inconsistent with the rights set out continues to be valid - so we do not have a regime that allows the judges to strike down laws.

But this power in Parliament to breach fundamental rights, and so fail to abide by New Zealand's obligations under international human rights law, is a power that must be exercised on an eyes wide-open basis.

The Attorney-General has to report on the risk that a particular bill before Parliament might be treading on hallowed turf, and the judges are given the obligation to do what they can when construing the language of a statute to adopt an interpretation that is consistent with those rights.

It is this last obligation that is the key tool under the NZ Bill of Rights Act.

It allows the judges, when ruling what a statutory phrase actually means, to do what they can to reach a solution that is consistent with human rights.

Given the fundamental importance of those rights, that seems obviously sensible.

But does it mean that a group of be-robed but unelected judges have taken over from the legislature?

Far from it. Parliament has conferred the eminently judicial role of protecting New Zealand from an inadvertent breach of human rights by providing that Parliament's words should be construed not to breach those fundamental rights unless there is no alternative but to reach that unhappy conclusion.

And the simple fact remains that Parliament can always overturn the effect of any judicial decision by passing further legislation using language that makes it abundantly clear that it wishes to breach fundamental rights.

That will ensure that Parliament confronts the fact that it is going against such important principles.

Given that the Human Rights Committee of the United Nations provides a forum for the actions of the New Zealand Government to be examined by a panel of lawyers for consistency with human rights standards, the real impact of the NZ Bill of Rights Act is that it allows that review be carried out by home-grown judges.

In a country that is proud of its exports, it is worth noting that the scheme has been adopted in several jurisdictions abroad.

The techniques invented by the drafters of the NZ Bill of Rights Act were copied by the Parliament of the United Kingdom as a central component of the major constitutional reforms of the late 1990s, which included the first modern-era enactment of a human rights framework in the form of the Human Rights Act 1998.

The central concern of the Westminster Parliament was that its legislation was reviewed for human rights compliance abroad - in the UK's case by the judges of the European Court of Human Rights - rather than by the domestic courts.

And so it adopted the New Zealand model as a method of bringing rights home to the domestic context.

The Irish Oireachtas followed the New Zealand model in 2003: its European Convention on Human Rights Act works in the same way, and was chosen in preference to an amendment to the Irish Constitution.

There has even been movement that allows one to mention "protection of human rights" and "Australia" in the same sentence, with statutes in the Australian Capital Territory and Victoria that take the model from this side of the Tasman.

Why this imitation? It could just be that the NZ Bill of Rights Act meets the test credited to Albert Einstein that "Everything should be made as simple as possible, but not simpler".

In other words, the act is a legislative pearl that other jurisdictions have concluded is an obviously good idea and should be copied.

So the 20th anniversary of the act coming into effect is something of which we can rightly be proud.

Kris Gledhill is a senior lecturer in law at the University of Auckland.