The issue of whether New Zealand should adopt a written constitution is one that gets an airing regularly. Sir Geoffrey Palmer has raised the issue again with the media reporting that he considers it time to consider the issue afresh. Whether New Zealand should abandon its distinctive ‘unwritten’ constitutional structure and place a written document at the centre of its constitutional arrangements is a very complicated issue. It involves assessing complex trade-offs and opens up controversial debates about the philosophical underpinnings of government power. However, I also believe that it is a debate worth having.

There are many aspects of the debate that I think ought to be expanded on and explained for the benefit of a lay-audience. In this post, I want to address one important preliminary point – does New Zealand need a written constitution?

I have phrased this question carefully. I am not asking what the relative merits of a written constitution are vis-à-vis an unwritten constitution. I am also not asking whether one form of constitutional government is better than the other. Those are important issues, but they need to come a bit later. What I am asking for the moment is whether there is something defective about New Zealand’s unwritten form of constitutional government that moving to a written constitution would fix.

The question is a preliminary one, as it sets the parameters of any serious debate. Identification of a serious problem with the unwritten constitutional form already goes a long way towards establishing the case for a written constitution, for example. Fortunately it is a question with an easy (and I think uncontroversial) answer. That answer is ‘no’. New Zealand does not need a written constitution. Our current, unwritten constitution operates very well and very effectively in practice.

The point here is really that our unwritten constitution does everything that we would want a written constitution to do. It constrains state power, so that governments can’t just do anything they like once they get elected. It promotes stability in respect of important values and ideals, so that things like fundamental human rights get the respect they deserve and aren’t easily over-ridden. And it confers legitimate authority on government institutions (such as Parliament and the courts) so that we have good reasons to believe that they deserve our respect. These are the basic functions of any modern constitution, and our unwritten constitution does each of them remarkably well.

The difference between written constitutions and unwritten constitutions is not what they do. It is how they do it. At a high level, written constitutions tend to set out and deal with state power in very precise, defined ways. Unwritten constitutions are more abstract and ambiguous, but make greater use of successful precedent and current practice. Each approach has advantages and disadvantages with respect to the other, but neither is inherently superior. If you strongly favour one approach over the other it will probably be a reflection of your personal views on the role of government in a modern society. But there is no independent yardstick against which to determine that one approach is just simply better than the other.

So we don’t need a written constitution. That's an important conclusions because it means that if you like the idea of a written constitution, you need to be very clear about why you hold that view. We shouldn't consider change just for the sake of it.  It's only when we get into the reasons behind calls for change that things get interesting, because then we might be in a position to decide that the benefits of a written constitution outweigh the inevitable drawbacks of losing our distinctive unwritten constitutional form.

Or we might not, but we will only know if we engage in well-informed debate that takes the advantages of our unwritten constitution seriously. If this is the sort of deabte that Sir Geoffrey has intended to start, then I look forward to being a part of it.