Sir Geoffrey Palmer said Harry Duynhoven's breach of the Electoral Act could be considered "trifling" and ignored by Parliament.
"The law does not concern itself with trifling matters," he told Parliament's privileges committee.
Sir Geoffrey is a former prime minister, a much-published constitutional lawyer who rewrote the Constitution Act in 1986, and an adviser to rich corporations on constitutional and administrative law and practice.
Nevertheless, the privileges committee, which includes lawyers Lianne Dalziel, Wayne Mapp, Winston Peters, Richard Prebble, Matt Robson, Metiria Turei and Margaret Wilson, threw out this argument.
Instead, a majority of Parliament opted for another Palmer suggestion: a fast-tracked retrospective bill to clear Duynhoven and let him keep his seat. A bare majority, Labour, Progressive and the Greens, extended that to cover the whole of Parliament for the whole of this parliamentary term.
Duynhoven's majority dropped, as Prebble tartly observed, from 14,930 at the election to an ignominious five in Parliament.
This move was possible only because Speaker Jonathan Hunt opted to get Parliament to pronounce before deciding whether Duynhoven's seat was vacant. The new law gazumped that process.
Hunt quoted the learned authority of Clerk of the House David McGee. And he was backed by lawyer-ministers who found ambiguity in the section of which Duynhoven ran afoul, which ousts an MP who acts or concurs in an act to obtain other citizenship. Under Dutch law he is deemed always to have been a Dutch citizen.
The layperson will struggle to find ambiguity. So did the august Solicitor-General, who was clear there was a breach. Under New Zealand law (Dutch law doesn't apply here) Duynhoven was out as of June 11 when he applied to have Dutch citizenship restored.
Parliament has been, Peters said, besmirched. You and I have to obey the law, even when we do not know what it is. Parliament says so. But for one of its own Parliament fixed it up.
Actually, there was a commonsense ground. The general law allows dual citizenship and the Electoral Act plainly allows dual citizens to be MPs if they are so when elected. To eject someone who acquires dual citizenship while an MP seems anomalous.
Or does it? If electors know or can find out someone has dual citizenship, they validate it by electing him or her. They can't validate a dual citizenship acquired after an election, except through a byelection. Nor can they do anything about list MPs, except to vote against the whole party.
National and Act would now resolve the anomaly by banning MPs from dual citizenship. As Prebble said, no one worries about decent Holland. But what about Cuba or Iran?
Fine words, though absent from their contributions to debates over the years, including last year when Parliament addressed the Duynhoven section.
Given that several MPs have dual citizenship, it will be interesting to see how hard they push this when they debate the substantive legislation to follow the Duynhoven bill.
The Duynhoven manoeuvre raises another issue. Retrospectivity goes to the heart of our democratic liberties.
The principle of non-retrospectivity bans prosecution for an activity that was not a crime at the time. And when a crime has been committed, the sentence is the one applying at the time of the offence, not one applied by subsequent law.
Non-retrospectivity upholds the principle that we may do everything that is not explicitly outlawed. That lends certainty to the law (though does not excuse ignorance of it).
But there is a let-out. Duynhoven's law does not take away a right from him. It confers one on him. Since no one else lost a right as a result, it is possible to excuse it - if you are of a mind to make exceptions for MPs.
Except that this is a class bill. The blanket coverage of the Duynhoven bill persuaded National, Act, New Zealand First and United Future that some other Labour MP or minister must be in the same boat. Who knows what important affairs of state that MP might - unlawfully - have signed off? But even so, as one National MP candidly put it to me, "Mums and Dads" are likely to see this as no voting matter, soon forgotten and no big deal.
So, as a minister scoffed to me, only a "purist" would have required Duynhoven's ouster and a byelection.
And that is the New Zealand way. When the constitution is an inconvenience, we go round it. Laws have been passed which in other countries, even Australia, would be found unconstitutional.
Yet constitutionality is fundamental to the rule of law which is fundamental to our democratic liberties. The Duynhoven doctrine derogates from that. The justice and electoral law committee might usefully ponder on this incident when it starts its inquiry into the constitution later this year.
There was another way for Duynhoven and Parliament. Its name is honour.
* Declaration: I hold two passports, New Zealand and European. I have never wished to stand for Parliament.