The rulings, one of which has yet to be explained, do not of themselves go to the validity of Australia's overseas concentration camp system. The three recent ones go to the power to detain indefinitely non-citizens when there is no country willing to receive them, to the power to deport non-citizens without reference to the courts, or to judicial findings made by the courts, and to the power to strip citizens of citizenship. The decisions recognise that detention, and lost rights of citizenship are or can be punishments, rather than mere consequences or incidents of bad behaviour. When they operate, effectively, as punishments, their imposition is a matter for courts rather than the executive government. It's a constitutional principle, flowing from the doctrine of the separation of powers.

Some of the rulings, or thinking behind the rulings, contradicts old cases. It was about 20 years ago, for example, that the High Court, by majority and with its fingers held to its nose, agreed that indefinite immigration detention was legal. This was in part because of the fiction that it was not a punishment but an incident of an incapacity to find a nation that would accept a person ordered to be deported. We know now that this is out the window. Stephen Gagelar, the new Chief Justice has said in court that most on the court now think that decision wrong. They will explain why later.

Perhaps 100 people, some with criminal convictions, are immediately affected, even if the department, with its customary churlishness and contempt for the judiciary has so far released only one. But the decision always seemed anomalous, seeming to authorise detention without trial, punishment without sentence, and unlimited power without accountability.

The departing chief justice, Susan Kiefel, was among the judges determining two of the three cases. So, one cannot describe the decisions as representing a change in direction because of the appointment of senior puisne judge Stephen Gagelar to take her place. It has been coming for a while.

But the moment may have its particular significance. The original decision - the Al Kateb case was in 2004 - when some judges on the court may have been overawed by the rhetoric and panic of the War against Terror, and thus inclined to allow executive government rather more discretion than in more normal times. The two decades since have given many of the judges ample reason to be cynical about executive grabs for power, and for decision making without process, transparency and accountability. Many of the judges have also seen ministerial and bureaucratic abuse of power at first hand.

Four decades ago, many of the judges on the court were seen as activists and would-be reformers, in part because they saw a growing imbalance between the powers of government (ever-increasing) and rights of the citizen (mostly seeming to decline). Under sustained assault from conservative politicians, particularly after the Mabo and Wik decisions, newer judges seemed to lose much of their appetite for judicial activism. That did not necessarily mean that they became very conservative, but an increasing number of decisions seemed to be confined to their facts rather than grand statements of principle. In more recent times, however, new appointments, even some made under the previous government, have seemed to become more outspoken, more openly conscious of the power of the court to affect modern politics and administration, and more concerned about the practical impact of its decisions. Gagelar, confident and one of the more powerful and liberal intellects of the court, may prove just the person to lead it into a new, or renewed, influence in public affairs.

The moment might also be symbolised by the fall from power of Mike Pezzullo, erstwhile secretary of the department of Home Affairs. One cannot blame Pezzullo alone for his department's overreach in refugee, immigration, police and national security matters, because he had ministers, including Labor ones, who had devised, or authorised, the policies in question. But he was undoubtedly an advocate of such powers, and generally an outspoken opponent of the idea that they should be closely supervised by judges and other forms of accountability. He was forever seeking extension of power - including into the creation of a national citizen surveillance system that would have put China's to shame, and wider and ever less transparent powers for police and ASIO officers, all predicated on increasingly more doubtful claims of drastic threats to national security. He developed his own paramilitary service and his own private intelligence establishment, as well as seeking to control (or as he would say "coordinate") the supposedly independent advice coming to government from ASIO and the AFP. He wanted everyone singing from the same hymn sheet, and made life difficult for anyone, in his department or out of it, who resisted him. Debate was not his forte. Nor management of billions in departmental appropriations - even if, from a political point of view, his assistance in creating a sense of panic, emergency, crisis and the need for stampede provided big dividends.

MORE JACK WATERFORD:

As we now know, if not yet in detail exquisite enough, this man given to lecturing his equals and his underlings about their duties under Westminster conventions was privately having irregular and improper communications with politicians and lobbying for party political outcomes that suited both his world view and his empire building ambitions. His fate is still uncertain, but it is manifestly clear that his day is done, and that this government does not want a replacement in the least bit like him. It might be too much to suggest that High Court judges, or their colleagues in the Federal Court were ever intimated by Pezzullo. But it is not too much to suggest that they breathe more easily in the knowledge that his reign - and the power and influence of his pessimistic world view - is over.

Given the political attractions of demonising people who seek refuge from war and persecution in Australia, and the long history of pretences, at enormous public expense, that the least concession will open the floodgates to an invasion of terrorists, paedophiles and criminals, one can predict that a calmer approach from the courts will inspire strong criticism. From Dutton down, and even from some battered Labor figures, some of whom carry our cruel refugee policies on their consciences, will come the cry that politicians, not "unelected" judges should determine the application of our immigration policies. That these decisions turn on some hard cases, of people convicted on terrorism, child sexual offence and sexual assault charges, will pander to the rich veins of prejudice in the community.

Are these the sort of people Australia wants? We will be asked. Does not the court's decision mean that Australia has lost control over who can stay and who cannot?

The recent decisions have little to do with the architecture of our immigration system. The threat of a boat people invasion is in decline, for the moment, anyway. That's a fact that might embolden the court in future refugee appeals without any direct reference to a new spirit affecting deportation and denaturalisation matters.

What may well bind them together is not so much a one-size-fits-all jurisprudence, but a fresh determination that immigration law, like general administrative law, is under the supervision of the courts. Confronting the way ministers and the department have long been trying to minimise the supervision of the courts and to maximise the power and the discretion of officials and ministers.

The courts have long been hostile to privative clauses - purporting to make administrative decisions unappealable, or appealable only on narrow grounds. Populist politicians - Peter Dutton, as a former minister for Home Affairs, would be the arch example, have decried the "liberalism" of judges and members of administrative appeal tribunals substituting their own views of what is appropriate for the opinions of elected politicians. His attitude, shared by other immigration ministers such as Scott Morrison, and prime ministers, such as Tony Abbott, has been behind the stacking of administrative tribunals with former Coalition apparatchiks likely to take a "firm" line and to respect the approach of the elected government.

Now would be a very good time to release some of the records of Operation Sovereign Borders, by which our defence force set out to encounter and drive away civilians seeking refuge in a rich stable nation free of war and communal strife. A nation which had, 75 years ago, helped pioneer the new conventions on public assistance to those displaced by war. And at a time when the national standard of living was perhaps a fifth of what it is now. Australians now better understand just what a fiscal, administrative and humanitarian disaster our Nauru and Manus Island system was but have yet to appreciate how it coarsened our civilisation, diminished our reputations, and deprived those who conceived it, those who implemented it, and those who defended it of moral authority and civic legitimacy. The histories, when written by our grandchildren, will be unsparing of all manner of collaborators, not least the media.

Australia's official hostility to refugees, and its policies of trying to locate boat people offshore, have become more popular abroad, thanks in part to the proselytization of Tony Abbott. Britain's Supreme Court, once called the House of Lords, is soon to rule on appalling schemes to send "illegal" entrants to Rwanda. Many European countries have attempted to repel boarders fleeing war, oppression and disaster, whether from Ukraine, Africa or the Middle East. The US perceives itself as being in a crisis with people seeking entry through Mexico, and Democrats are responding by re-opening talks about completing a wall. It goes without saying that climate change is already behind much of the mass movement of people from Africa to the Mediterranean. It could become a fresh problem for Australia from rising sea levels in the Pacific and parts of Southeast Asia, or, more probably, from an increased rate of natural disasters in our region.

Now is a time for Australians to be calmly considering how it is going to deal with such challenges. And how, for that matter, it is going to run programs in some tandem with general immigration levels, and our education export industries. Perhaps they are not to be run on principles established after the displacements of World War II (though I do not see why the principles of compassion and help should not prevail). But if so, no more should the operating principles turn on the fears and suspicions of the Cold War, the so-called War Against Terror, or militant Islam. These are not, any longer, the primary factors generating the streams of refugees. It's drought and natural disaster. Local violent competition for resources. Corrupt, authoritarian governments and civil wars. Nationalism and ethnic cleansing.

It is of course true that the more Australian resources are focused on assisting displaced people at the front line, the lower the pressure on our own population. We are not faced with being overwhelmed or with any loss of our wealth or standard of living. When we see it as an opportunity rather than as a problem or a crisis, a potential source of growth and security rather than as a threat, we might be inspired to realise that tackling other pressing issues with a sense of purpose is not an unpleasant sacrifice but a necessary foundation for richer and happier lives.