The Federal Government has effectively been told that it can detain and transfer asylum seekers against their will even when they've never entered Australian territory, writes Michael Bradley.

The High Court has handed a victory to the Government in the case of the 157 Sri Lankan asylum seekers. In doing so, it's trashed any lingering hope we might have had that asylum seekers have human rights in the eyes of Australian law, and left some disturbing implications for the future.

On June 29, 2014, an Indian flagged vessel carrying the Sri Lankans was intercepted by Australian Customs 16 nautical miles from Christmas Island and four miles outside Australian territorial waters. The Sri Lankans were Tamils, and claim to be refugees.

The boat was unseaworthy, and the 157 were taken onto an Australian ship. They were detained there while the ship sailed to India. It stayed just off India until July 22, when the Immigration Minister directed it to the Cocos Islands, which are Australian territory, where the 157 were finally disembarked.

What happened to them after that, we do not know. We do know that the decision to ship them to India was made by the National Security Committee of Cabinet, but we aren't allowed to know why.

The High Court was asked a deceptively simple question: did the Government have power under the Maritime Powers Act (MPA) to do what it did, or was the detention at sea unlawful? The Court, by a 4-3 majority, said the Government's actions were all good.

Unfortunately, the case before the High Court involved very few agreed facts. The 157 had departed from India, but there was no evidence about their circumstances while in India or what might happen to them if they were returned to India (most importantly, whether they might then be deported back to Sri Lanka).

The ship was intercepted outside Australia but within a 12 mile "contiguous zone". Australian law doesn't apply generally in that zone, but the MPA gives our maritime forces certain powers that they can use in the zone to prevent contraventions of Australian law. In this case, it was assumed that the 157 intended to enter Australian territory without valid visas, in contravention of the Migration Act.

Having formed the reasonable suspicion that a contravention was intended, the Government had the power under the MPA to detain the 157 and take them to "a place" anywhere in the world. The NSC decided on India. Australia had no agreement with India about taking asylum seekers, and India never agreed to take them.

The High Court's decision came down to a narrow question: at the point when the Government decided to take the 157 to India, was it necessary that they had a right or permission to actually land there? The minority of the Court said it was. The majority, however, decided that the Government only had to make a "probabilistic assessment" that there was a "reasonable possibility" that India would agree to take them. The assessment of that was a matter for the Government, not the courts. The bar has been set very low: the Government can choose to have a crack at any destination, provided it doesn't know at the time that there's no way that country will say yes and it isn't just randomly guessing without any real basis. But, of course, the Court didn't know and we are not permitted to know whether in fact the Government had a strong basis for thinking India might agree.

In this respect, the majority of the Court placed itself in a Catch-22; it set a limitation on where the Government can send detainees, but implicitly accepted that the Government can satisfy that burden by simply saying "we had our reasons". And that's the end of it.

This is a strange retreat by the Court from its often asserted authority to exercise genuine oversight of Government decision-making, particularly in areas that impinge on basic human rights. It is compounded by the scant attention that the whole Court paid to the underlying purpose that gave the Government the power to cart the 157 around the ocean for a month. These powers are extraordinary and draconian; they allow physical detention and carriage of people, against their will, by Australian authorities when they've never even entered Australian territory. It's basically legalised piracy. Which is OK, if for a legitimate purpose.

The purpose is to prevent them from entering Australia without a visa. The detention powers can only be exercised to achieve that purpose; not to punish them, or to deter others. Given that Australia had agreements in place with PNG and Nauru and could have taken the 157 to either place with infinitely more certainty than it could ever have about India, it's strange that the Court didn't consider whether it could come to the conclusion that the decision to go to India was impracticable and unreasonable.

The end result is that the High Court has effectively vacated the field and given the Government carte blanche to do what it likes to people who it picks up in the 12 mile contiguous zone. That includes Australian citizens, by the way.

Just in case it lost, the Government amended the MPA in December to make it crystal clear that it can send people anywhere, with unlimited attempts, detaining them for as long as it takes, and that it doesn't have to consider its international obligations (such as the "non-refoulement" obligation to not send a person back to a place where their life is at risk).

As it turns out, the amendments weren't needed. The High Court confirmed that those international obligations (arising under agreements like the Refugee Convention and the Convention on the Law of the Sea) aren't part of Australian law. We can legislate them into irrelevance, as we have done in respect of asylum seekers.

The High Court's decision in this case isn't necessarily wrong as a matter of law; technically, it's a narrow majority ruling on a narrow question in very specific circumstances. Armed with more or different facts (for example, if there was evidence that the 157 would be at risk of deportation to Sri Lanka once they landed in India), the Court might have gone the other way. However, the case afforded the Court an opportunity to assert a more robust judicial authority to hold the executive arm of government to account when it is exercising extreme powers that directly interfere with what we all understand to be a basic human right: the freedom of movement.

It's extremely unfortunate, in my view, that it didn't take that opportunity. Consequently, we've taken another step towards authoritarian rule.

Michael Bradley is the managing partner of Marque Lawyers, a boutique Sydney law firm.