KEY POINTS:
It was conceived at a time when the world seemed to be flirting with the madness of flirting with Armageddon.
A time when the words "cruise missile" added a new dimension of horror to the arms race and raised the spectre of nuclear weapons being used on battlefields in Europe's backyard.
A time when America's president relived his Hollywood past by mooting a "Star Wars" missile shield over the United States.
It was against that early 1980s backdrop that the Labour Party in Opposition sought to ban nuclear-armed and nuclear-powered ships from New Zealand ports. The party's 1984 election manifesto promised to write the policy into law.
But it was not until December the following year that the New Zealand Nuclear Free Zone, Disarmament and Arms Control Bill made its parliamentary appearance.
It was delayed because David Lange and other senior Cabinet ministers had been trying without success to find some way of placating the Americans, for whom it was the last straw.
The left wing of the Labour Party was correspondingly suspicious that the bill might end up being worded in such a way as to weaken the anti-nuclear policy or create loopholes.
According to Lange, it was Helen Clark, then on Labour's backbenches, but chairwoman of Parliament's foreign affairs select committee, who examined the bill from all angles before giving the left's seal of approval.
Enshrining the policy in law was a political masterstroke. It broke foreign policy convention by forcing any future Government to go back to Parliament if it wanted to reverse the policy.
But 20 years on, the act reads in part like some Cold War relic. Some provisions now sound faintly ludicrous, others are dated.
As a moral stand against the Cold War nuclear arsenals of the superpowers, the law may still fill New Zealanders with pride. But in the age of the terrorist, nuclear war is now waged at a micro-level.
As it was, the ink was barely dry on the legislation before Ronald Reagan and Mikhail Gorbachev took the first steps towards reducing their arsenals of nuclear ballistic missiles.
The thaw had begun. The Berlin Wall tumbled. The National Party won office in a landslide. The Soviet Union collapsed. The Americans took tactical nuclear weapons off their warships. A portion of the law was instantly redundant. The argument shifted to the safety of nuclear-powered vessels.
National established a panel of scientists to sort fact from myth. Among its findings was that the patients in Auckland's hospitals released twice as much radioactivity from their bodies as the entire fleet of the United States Navy.
If scientific logic had been the sole factor, National would have amended the law. But by the time the scientists produced their report, National had slumped in the polls. The report was quietly shelved.
National had discovered that while the law remained a fiction in terms of isolating New Zealand from the ravages of nuclear war or accident, its ban on port visits by nuclear-armed or powered warships had an influence far beyond the nuclear debate.
The law had become a symbol of the moment the nation came of age and threw off the last colonial shackles.
After the Muldoon years of genuflecting to the White House and Whitehall, the anti-nuclear policy was the two-fingered salute of an obedient child turned stroppy teenager.
That symbolism still glows with the intensity of fuel rods in a nuclear reactor. Politicians tamper with it at their peril.
That did not stop National revisiting the policy, sometimes head on and sometimes obliquely.
John Key has put an end to that.
National failed because it could not isolate the nationalistic element in the law from the negative effect on defence policy that it wanted to address.
It failed because it could not offer a convincing reason why the law should be changed.
Voters have long ignored its crippling effect on the armed services. Anzus was consigned to the shredder. The public cared little.
Being nuclear-free turned out to be pain-free.
Almost. Canberra got its revenge by twisting Labour's arm into buying Australian-built frigates rather than cheaper European ones.
Doors slammed shut in Washington and London. If anything, this increased the patriotic fervour. Washington might have done better to have not retaliated at all or retaliated in a fashion which jolted New Zealand out of its moral righteousness.
Had the Americans retaliated with trade restrictions the Government might have thought again about inscribing the anti-nuclear policy in the statute books.
As it stands, the law is not all its proponents cracked it up to be.
Under international maritime law, the Americans or the Russians could sail nuclear-armed or powered ships through Cook Strait at will if they felt so inclined. A ship in distress carrying nuclear waste could legally enter New Zealand territorial waters to seek help.
Is the law still untouchable? Opinion polls in recent years have registered a growing willingness to accept nuclear-powered ship visits, although the majority still opposes them. But it is the depth of feeling, rather than the breadth, which politicians have to gauge accurately.
That aside, if National changes its mind again and tries to revisit the anti-nuclear policy, it will now need the backing of coalition or support partners. Act is the only party to express any desire to change the law.
In the final analysis, National need do nothing because the law is becoming increasingly irrelevant where it really matters.
For the best part of 20 years, it was the roadblock to restoring political and defence ties with Washington back to some degree of pre-1984 normality.
The US Navy would not accept restrictions on how and where it sent its vessels. It also could not get over the slight of an old ally not only no longer welcoming its warships, but writing that rejection into the law.
But a significant shift has occurred in Washington's stance in the past year or so. It now accepts that there is no chance of any New Zealand government changing the law. Instead, it is treating the law as an obstacle around which the two countries can navigate.
Any return to the pre-1984 status quo is anyway both impossible and unthinkable. New Zealand's foreign policy, while necessarily constrained by the country's size, is nevertheless far more independent than it was. It seems unlikely that a John Key-led National government would want to turn back the clock.
In that sense, the anti-nuclear law has done the job the Labour left wanted it to do.
