Passport cancellations are one of the few tangible and public measures of how Australia’s going in the fight against terrorism. ASIO made the latest number of passport cancellations public last week, when it tabled its Annual Report to Parliament.

The report states that 62 Australian passports were cancelled over the past 12 months to prevent Australians from travelling overseas to engage in terrorism. That figure is down one third from a peak of 93 cancellations last year—which coincided with the rise of the so-called ‘Islamic State’ or Daesh and its call for foreign fighters—and is back to the 2013-14 level, when 45 passports were cancelled. Numbers haven’t yet dropped down to pre-Daesh single-digit levels.

So while Daesh and other Islamist groups are still attracting foreign fighters, the numbers seeking to travel have waned with the fortunes of those groups. The ASIO report tells us that the decline in cancellations is because fewer Australians are seeking to travel to fight in the Middle East. But there’s still a relatively high number of cases, demanding a lot from Australia’s counterterrorism resources.

Passport cancellations remain a complex and sometimes confusing issue. One of the most prominent cases is Oliver Bridgeman, whose passport was cancelled in February while he was in Syria, soon followed by the issue of a warrant for his arrest. After six months silence—including speculation he’d been killed—Bridgeman’s lawyer says he’s alive and still overseas.

Bridgeman and his family say it’s all a misunderstanding: he’s just a healthy, happy, young surfer and school-leaver working for a children’s charity in Syria, and the government’s actions have left him stranded in a war zone.

Bridgeman provides a useful case study on Australia’s passport cancellations, how and why these can be used, and what happens after.

So here are 10 things you need to know about passport cancellation.

1. Only the Minister for Foreign Affairs can find someone ineligible to hold an Australian passport. Cancelling a passport is a big deal—as befits an action to deprive an individual of freedom of movement—and is out of the hands of individual government agencies and appointments.
2. The recommendation must come from a ‘competent authority’— a government entity with appropriate expertise to make the judgement behind the recommendation. In the case of Bridgeman and many others whose passports have been cancelled on terrorism grounds, the judgement was in the form of an ASIO security assessment made by ASIO’s Director-General.
3. The security assessment is the overall judgement. The Bridgeman family’s lawyer has challenged the information in the security assessment. But the advice to Bridgeman isn’t required to include all the supporting detail—including classified information—used to make the assessment or the Minister’s decision. That has sometimes proven contentious and has been subject to review and legal judgement—including in the High Court—but found to be appropriate.
4. The cancellation can be based on anticipated future behaviour. A passport cancellation may be preventative. The test in the Australian Passports Act 2005 is ‘suspects on reasonable grounds’ that the person would be ‘likely to engage in conduct’ contrary to security, or might breach Australian law. That’s different from a criminal charge, since no crime need be committed. In addition to protecting Australia’s interests, this measure also helps uphold Australia’s international obligations, such as not exporting terrorism.
5. Until recently, security-related passport cancellations were rare. The conflict in Syria has attracted a higher proportion of Australians per capita than any other country. Before Syria, passport cancellations were few: seven in 2011-12 and 18 in 2012-13, according to ASIO. In August, Minister Assisting the Prime Minister for Counter-Terrorism Michael Keenan said there had been more than 180 since the Syrian conflict began—including around 50 offshore like Bridgeman—with more every week.  
6. It can be appealed. Bridgeman’s family have lodged an appeal to the Administrative Appeals Tribunal for a merits review. A request could also be made to the Federal Court (and High Court of Australia) for judicial review of the decision.
7. Government authorities are constrained in talking about individual cases due to privacy, legal process and protecting classified information. With the appeal process underway through the AAT, along with the separate criminal case, it’s unlikely that authorities will provide commentary outside the legal process.
8. Citizens retain a right of return. That’s possible without a passport. In Bridgeman’s case, he could return to Australia under a temporary travel document. But having travelled to a conflict zone—and possibly into a declared area—there are security and safety issues at play should he attempt to leave or for any Australian consular staff to contact him.
9. Arrest warrants are different and have their own high threshold. An arrest warrant results from evidence acquired through criminal investigation. To have an arrest warrant issued, the AFP must have a brief of evidence that’s deemed sufficient to lay criminal charges by both the Director of Public Prosecutions (DPP) and the issuing magistrate. Should Bridgeman return to Australia and face prosecution, we would then have the opportunity to see this play out in court.
10. It doesn’t necessarily remove the threat. Passport cancellations appear to be an effective inhibitor of terrorism. For those remaining in Australia, in particular, community and professional support may assist a move away from violent extremism. But being denied the ability to leave Australia on their own passport might also encourage a want-to-be foreign fighter to use someone else’s passport, as with Khaled Sharrouf, or refocus their activities back to Australia, as may be the case with Numan Haider. Earlier this year ASIO advised that around 200 Australians were actively supporting Islamic State from home.

In the Bridgeman case, we know that ASIO and the AFP have investigated his actions and associations and consider that they separately meet the threshold for passport cancellation and arrest on terrorism grounds. The Foreign Minister, the DPP and a magistrate agree. All of that remains subject to due process, and the protection of rights under the law. And that makes all such decisions tricky—the application of the law is relatively straightforward when a crime is committed, but anticipatory and protective measures have a different threshold and host of complicating factors.