There has not been a more obvious breach of the Cabinet manual this term than Winston Peters' failure to abide by collective Cabinet responsibility over Covid-19 restrictions - but nor has there been a breach that matters less.
The differences between Prime Minister Jacinda Ardern and Peters, her deputy, does not affect the stability of the coalition between Labour and New Zealand First.
It does not affect the coalition relationship which has endured more damaging differences than this one. It has been an informally managed disagreement that both parties get something from.
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It is a disagreement about the speed of the exit from alert level 2, not a disagreement about the end result.
Ardern continues to represent the actual decisions made at Cabinet, and remind the public that as the leader of the country, she is having to find a balanced way through between the health and economic imperatives.
Peters continues to advocate for the decisions he wishes Cabinet had made, making it more likely that his New Zealand First Party gets credit for any accelerated exit rather than National.
And obviously that is all about the electoral survival of New Zealand First, which is under threat in most political polls.
Every time National's Todd Muller points out that New Zealand First is saying something different to Ardern, it amplifies the role of New Zealand First in agitating for a speedier exit.
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This is more than political posturing. Even Ardern has accepted the need for a speedier exit, bringing forward the decision about exiting level 2 to Monday next week.
Previously, that was the date Cabinet had set to review the rules within level 2, not leaving it altogether.
Ardern is happy to be seen as the more cautious leader of Government. She has largely accepted the advice of director general of health Ashley Bloomfield, although she rejected his recommendation for bars to open two weeks after restaurants, rather than the one week Cabinet settled on.
The Cabinet manual says the principle of collective Cabinet responsibility underpins the system of Cabinet government, and that issues that are debated confidentially in Cabinet meetings must be supported by all ministers, no matter what their view at the time.
Peters, in repeatedly advocating a move to level 1, is not supporting the decided timeline and so is in breach of collective Cabinet responsibility.
But New Zealand First having differences with its Labour partner is hardly a new phenomenon either.
It has stymied Labour's efforts to find a taxpayer-funded solution on Ihumatao, it has stymied Labour's fair pay agreements, its moves to repeal three strikes legislation and its bid to get a capital gains tax.
They have been irritants however. They have not involved a breach of the coalition agreement or any double-crossing.
More damaging have been the differences between Ardern and Peters on managing the China relationship, which led to Ardern having to clean up Peters' diplomatic messes more than once.
He and Ardern could decide to invoke the "agree to disagree" measure allowed for under the Cabinet manual, which is a formally managed disagreement on Government policy instigated by the 2000 Labour-Alliance Coalition.
It is rarely used but New Zealand First invoked it last November in order to oppose the already legislated 11.46 per cent tobacco excise.
This disagreement is about a decision yet to be made, not one that has been made.
But in the end, the Cabinet manual is like the Bible. It can be whatever you want it to be, depending on the discretion of the Prime Minister.
It can be a black-letter rule book; or it can just be a guideline.
A breach can be used to dismiss a minister or alternatively to reprimand them, depending on what the PM wishes.
Or, as Peters knows full well, it can also be ignored.