Australia has some of the strictest border laws in the world. The immigration minister has some of the broadest, and least reviewable, powers of any of his global equivalents. The shambolic Djokovic affair has confronted Australians with the true extent of those powers, and many are bewildered.

Discretionary powers under the Migration Act enable the minister to cancel a visa – in some circumstances without affording due process – because, a “person’s past and present general conduct” suggests “the person is not of good character”; because “there is a risk that” the person’s presence represents “a danger to the Australian community … in any … way”; or because the person “might be … a risk to the health, safety or good order of the Australian community.”

The merely contingent and speculative quality of the assessments that can trigger the minister’s cancellation powers were highlighted in the Djovokic case. The minister did not have to consider whether Djovokic’s presence in Australia would in fact encourage anti-vaccination sentiment. It was enough that he be satisfied that it “might”.

Considered in the context of the other provisions – which allow the minister to cancel a visa because of reasons including being suspected of, or posing a risk of committing, various types of criminal activity; providing incorrect or untrue information; or contravening a visa condition – there is no clear justification for the breadth of these powers.

The problem is more acute because these drastic powers ultimately rest on the subjective state of mind of one person, with severely limited grounds of review by the courts. Leaving aside the Djokovic case, it may be asked, could one have their visa cancelled because the minister disagrees with their religious or political opinions? As the Australian Lawyers Alliance pointed out this week, the extraordinary powers “could see other high-profile visitors to Australia refused entry in an attempt to suppress alternate views.”

These considerations lead the UN Special Rapporteur on the Human Rights of Migrants to say that the powers granted under the Act could “risk a politicised and biased use of controls, and be in violation of the principles of legality”, because they were not matched with “the appropriate level of oversight to the country’s judiciary”. As the president of Liberty Victoria observed in the wake of Djokovic’s expulsion: “One danger of largely unfettered discretions, or ‘God powers’, is that decision making just becomes political and populist … eroding the integrity of the executive and the rule of law.”

Remarkably, the minister may overrule a contrary decision of the administrative appeals tribunal, while the minister’s decision is subject to severely limited review by the courts. There must be proof that the minister’s decision was infected by an error of law to overturn it – a notoriously difficult task, as Djokovic discovered.

Many refugees and asylum seekers have felt the full force of these powers over the years – finding themselves denied access to Australia – for reasons much less compassionate, in circumstances much more inhumane, and with consequences more drastic, than Djokovic.

Djokovic’s standing, resources and mouthpiece kept him on the front pages for a week. But what of those who don’t have those advantages, or Djokovic’s money and support?

What of the refugees and asylum seekers, fleeing genocide, war and violence, only to be detained once they arrive in Australia, possibly indefinitely, in cruel and hopeless conditions, with lengthy court delays and limited access to legal representation? Just think of those still at the Park hotel, essentially forgotten until Djokovic briefly shared their confinement.

Djokovic’s case was dealt with from start to finish in less than a week. Many refugees and asylum seekers wait months, if not years. Djokovic was allowed to leave detention while his case was pending, despite its brevity. Many refugees and asylum seekers remain locked up for much of the process. Djokovic had swift and consistent access to high quality lawyers and was allowed to meet them face-to-face. Many refugees and asylum seekers struggle to find representation and rarely meet their lawyers face-to-face. Djokovic commanded news feeds for weeks (and still does). Most of those in detention languish unnoticed.

For decades, Australians have tolerated – even encouraged – policy choices about immigration controls that favour real or imagined concerns about security over humanitarian principles.

The sorry saga of Djokovic’s visa is a vivid demonstration – if more be needed – that we have allowed too much discretionary, and essentially unreviewable, power to be concentrated in the hands of one person.

As John Adams observed, “Power must never be trusted without a check.”