The case of the three environmental activists who boarded the Japanese whaling vessel, the Shonan Maru 2 last week has divided opinions over the nature of their offence and what treatment they should receive.

After negotiations between the Australian and Japanese governments, the men were transferred from custody on the Shonan Maru 2 to an Australian Customs ship and returned to Australia. But many social and media commentators have suggested that as the activists’ actions amounted to piracy, they are not worthy of Australian government support.

Public opinion has been split, with an online poll conducted by the ABC’s The Drum running at 60% against government support for the activists while a similar Fairfax news one had 68% in favour.

There are several issues arising from this discussion: why do we consider some illegal actions to be punishable and others forgivable, or even commendable?

Firstly, let’s settle the issue of piracy. To describe activism at sea as piracy – or even terrorism, as suggested in one online news outlet (MSN) is wrong and irresponsible. The Forest Rescue activists were not armed, the Shonan Maru 2’s crew was. The activists’ aim was not to harm the crew of the Shonan Maru 2, nor steal property, nor hold anyone or anything to ransom: it was to stop an action they deemed to be a greater crime than the one in which they were engaged – boarding a ship without consent.

Under the UN Convention on the Law of the Sea (UNCLOS), piracy constitutes “any illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or the passengers of a private ship …” The Sea Shepherd crew engaged in trespassing, certainly, but piracy, no.

Can trespassing ever be deemed right? In 1996 four activists from peace organisation Ploughshares broke into the British Aerospace hangar in Lancashire. Their aim was disabling a BAE Hawk military jet, due to go to the Indonesian military for use against the East Timorese.

The activists, all women, caused £1.7m worth of damage to the aircraft before they were arrested. At their trial they maintained as their defence that their actions, while illegal, were perpetrated in order to prevent a greater wrong, the British government’s complicity in genocide. They were acquitted of all charges by a jury.

The greater wrong in the case of the whaling activists is the slaughter of marine mammals, protected under international law by Article 65 of UNCLOS.

This raises the question of what constitutes ethical action, even though it may be illegal. Ethically, these activists acted on the maxim that an action is right if it prevents a wrong. This is the same theory that underpins Thoreau’s famous dissertation on civil disobedience: that a citizen has a duty to act in contravention of the law if in so doing he or she is acting for the greater good.

It is also instructive to compare this case to that of Julian Assange. Ironically, online poll responses indicate that many of those calling for the whaling activists to face trial for piracy have also called for the Australian government to intervene on Assange’s behalf.

Twelve months ago, 85% of respondents to a Drum online poll and 82% of Fairfax respondents believed Assange should receive government assistance. What’s more, 67% of respondents wanted Assange named Australian of the Year.

Assange is accused of crimes (sexual assault in Sweden and potentially treason in the US) under the legal statute of sovereign nations rather than in non-territorial waters which come under international law. Why is he seen as worthy of government protection (not to mention the country’s highest civil honour) while the anti-whaling crew are accused of piracy?

Wikileaks deals with human society and uses computer technology to expose what it sees as wrongs by governments. Sea Shepherd deals with marine wildlife and uses direct action to expose what it sees as wrongs by governments.

But urbane, well-spoken Assange is seen as professional, and therefore a victim of government conspiracy rather than perpetrator. Scruffy, outspoken environmentalists are viewed as extremists, and therefore potential criminals. Yet trespassing is a far lesser crime than treason, regardless of the ideals for which either crime is committed and irrespective of whether either alleged crime is ever prosecuted in court.

Direct action at sea will not end whaling. Only negotiations between governments based on scientific and legal arguments will do that. But direct action ensures that the issue remains in the public domain and keeps pressure on governments to act.

Acting outside the law for the greater good is always dangerous practice, but where the public and media believe that we can pick and choose our outlaws based on how they look and whether their ideal is government transparency or saving marine mammals, it becomes even more of a lottery.