Mike Hosking: von Metzinger family's deportation tugs at heartstrings - but rules are rules

The von Metzinger case is not the first of its kind. It won't be the last. But it's a quintessential example of the classic immigration story gone bad, while tugging hopelessly at our heartstrings.

The family is being booted out of the country tomorrow. Their residency requests and appeals have been denied on health grounds.

Their youngest, Ethan, 15, has kidney trouble, and as a result may well need the help of the New Zealand government: read taxpayer-funded health system. As we know, because we have been here before, the rules are fairly clear.

Medical issues; long term, ongoing medical issues, will trigger the ticket home. In this case, there is no shortage of sympathy. One piece of reportage got the whole violin section out.

The older sibling has a dream of becoming a doctor so they can give back to the country they love. The family has offered themselves as kidney donors. They've offered to pay the bills for a transplant if its needed.

They've also argued that the young man concerned hasn't needed major medical attention for years, and it's possible he may never need a transplant. And there has been the obligatory petition, signed by more than 25,000.

So, a very, very good case if this was up for a vote. But immigration does not work that way, and nor should it.

It is, of course, a very good reason as to why we have the rules we do. And they're the rules you find in a very popular country. We must never forget, there is a reason these sort of families come here. Why wouldn't you? It is one of the greatest countries on earth.

And as a result of that, we have the ability to put rules in place, and one of the rules is you're not arriving with a pre-existing condition. As a result, you're not potentially burdening the public system.

And why, despite the arguments, the petitions and the offerings, are we still booting them out? Well that is the key point here: precedent.

As sympathetic as we may be, as commanding of our attention their individual story may be, the moment you make an exception, the floodgates open. Do it once, you do it 100,000 times - and that is a risk we can not take.

However, there could be a twist. Last resort cases always end up on the Immigration Minister's desk ... we have a new minister (Iain Lees-Galloway). And we have a Government seemingly obsessed with being nice. Playing the good guy, looking to dabble, if not swim, in social largesse.

It'll be interesting to see if this story tugs the minister's strings. And that fatal exception is made ... I hope not.

Not for the family (who doesn't feel bad for them?) but for the precedent, which is what we all must live with well after the von Metsingers are gone.