The chief check on them is Parliament. We are fortunate, indeed, to live in a country where we elect the people who sit above the police. Their ultimate bosses are our representatives elected by us.
That's how a democracy works.
Of course, the police also have the power to investigate members of Parliament. MPs can't be above the law.
Now here's where it gets tricky.
There have been places and times where the police have done that willy-nilly.
That gives them a sway and a power over the very people who should be keeping them in line.
We must always guard against that. It would be intolerable if the police - in secret - were to hold sway over MPs.
And so it is a Very Big Deal if the police receive a complaint about an MP.
I would expect, no, demand that they immediately advise their direct boss - the minister and ultimately the Prime Minister - that an MP is under investigation.
Not to do so is to leave police bosses open to the charge that they are interfering in parliament.
The minister and Prime Minister need not do anything. That's up to their judgment. But they must be told so no accusation can be made against the police.
It's very tricky for the police. I suspect, if anything, they are going to lean towards charging the MP - it's better the court process decides guilt or otherwise, especially if the charges are serious. The police can't allow the perception they take it easy on their political bosses.
TV One has reported that police were investigating Sabin in August last year.
It's inconceivable to me that they would not have told their minister and the Prime Minister.
It's especially important that they would do so with Sabin because he's ex-police and on October 22 he was elected to chair the law and order select committee.
That's the select committee that scrutinises police performance on Parliament's behalf.
Hang on. According to One News the chairman was under police investigation. And the Prime Minister didn't know?
Someone isn't doing their job. And we have a right to know who has let us down.
Our parliamentary democracy and justice system were reportedly compromised.
Anyone could see how our Parliament was conflicted and potentially corrupted.
Parliament meets this week for the first time this year. John Key has some explaining to do.
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