Opinion - It is still known to some of Parliament's older hands as 'the Maharey Rule.'
Steve Maharey, newly appointed Social Development Minister under Helen Clark, excused one of that government's changes of tack when challenged about the mismatch between his opposition rhetoric and his actions by breezily saying it was 'just the sort of thing you say in opposition'.
It was a burst of admirable frankness, and as such has been celebrated ever since.
There is more than a whiff of the Maharey Rule about the Labour-New Zealand First-Green government's change of tack on the Trans-Pacific Partnership agreement, and specifically the investor state dispute settlement (ISDS) rules.
Previously, these were a threat to New Zealand's sovereignty, according to the rhetoric of all three parties.
They were certainly the main source of the rage exhibited by anti-TPPA activists who protested in the streets about the agreement in early 2016.
Now, they are things that the government will still try to get removed or watered down, but there is an implicit acknowledgement in the rhetoric from Prime Minister Jacinda Ardern that those clauses will almost definitely stay in the agreement.
It is a long, long way from calling them a threat to sovereignty.
That agreement - dubbed "TPPA-11" by officials and politicians, and "the Zombie TPPA" by anti-trade activists after US President Donald Trump pulled his country out of the talks - will feature at the APEC meeting in Da Nang, Vietnam, next weekend.
Ms Ardern and Trade Minister David Parker announced the shift in stance at her first post cabinet press conference on Tuesday, but the announcement was downplayed.
Gone was any mention at all of how bad it would be if foreign multinationals are able to sue the New Zealand government (they can now, in fact) and there was certainly no mention of that "sovereignty" word, let alone any threat to it.
Perish the thought.
And this shift was dwarfed by the changes to rules around foreign investment in New Zealand's housing market.
This made a bigger splash - deliberately so, even though - as Parker conceded on RNZ the following morning - it will make little difference to current house prices.
Parker's bigger point, though, is a valid one: if any restrictions are to be put on such investment, now is the time to do it so it does not cause any significant problems.
It is a preventative measure, aimed at giving the Auckland property market - next time performs its well-known impression of an over-indulged toddler who's given red-coloured Halloween lollies - a bit of a nudge.
As such, it is also a rebuke to the outgoing National government, which didn't really want to look at the extent to which offshore purchasers were driving the hyperactivity.
There was a marked reluctance to act in 2014 when it was clear the housing sector was in serious need of quiet time: then-prime minister John Key wanted to be re-elected and his year was dominated by selfies in shopping malls rather than significant policy shifts.
The refusal to even look at how much the market might be driven by offshore money - National only very reluctantly agreed to collect such data - was immensely telling and it has given Ms Ardern ample opportunity to score political points on the issue.
The changes will, however, have little immediate effect.
The bigger, more immediate question is going to be how well the government's support base is going to accept what amounts to a very large cave-in over the TPPA and "sovereignty" issues.
As well, of course, as the evergreen, ever-applicable Maharey Rule.