Given yesterday's announcement by the Prime Minister that his Government would legislate within weeks to revoke Australian citizenship from dual-nationality terrorists, it is worth revisiting three Interpreter pieces on whether this is a useful weapon in the fight against terrorism. First, here's a February 2015 piece by former senior Australian immigration official Peter Hughes, now with the Crawford School of Public Policy at ANU, who is against the proposal:

To deal with the jihadist problem, the Government already has available to it criminal sanctions as well as the ability to withhold or cancel travel documents. So what difference would it make to the jihadist cause if the Australian Government could revoke Australian citizenship for dual nationals?

In practice, it would likely be a very limited tool. There is little or no public information which tells us whether or not the jihadists about whom our security agencies are concerned are dual nationals. If they are not, the proposed change in the law would be irrelevant...

...Even if the citizenship of some dual nationals of concern in Australia could be revoked, this does not necessarily mean they would leave Australia. One course open to them may be to rid themselves of their second citizenship by renouncing it so that they were no longer dual nationals. In some cases, foreign governments refuse to accept their own nationals back if the person concerned does not want to return voluntarily.

If the person is outside Australia when their citizenship is revoked, return to Australia is prevented, but the Government already has some capacity to prevent this with denial of Australian travel documents. Either way, the individual would be free to pursue extremist causes and political violence elsewhere.

The Lowy Institute's Rodger Shanahan sees one often overlooked reason for this proposed legislation:

The possession of Australian citizenship rightly imposes limitations on how much information Australia's spy agencies can collect, and perhaps more importantly who they can share it with. There have already been legislative amendments to strengthen the intelligence-collection powers of these agencies, but dealing with non-citizens gives them much greater flexibility in sharing information.

So, rather than dual citizens simply becoming someone else's problem or able to undertake violent actions elsewhere, such a move may actually free up Australian authorities to address the problem by sharing information on foreign fighters or terrorists who were formerly Australian citizens.

This may simply mean that the former dual citizen can be arrested and jailed, or deported to their remaining country of nationality. But it may also mean they are killed in a counter-terrorist military operation. In fact, there has been criticism in the UK that people stripped of their citizenship have been killed in drone strikes shortly after, and that the information that enabled their targeting was only released to the US after they were no longer UK citizens. I think this is the more appropriate discussion to be having, rather than a civil libertarian one.

Here's Peter Hughes again in August 2014:

Some years ago there were calls to revoke the Australian citizenship of suspected World War II war criminals in the hope that this would get them out of the country. We 'knew' they were guilty but couldn't actually prove it through a criminal justice process, so it was argued that an administrative decision under the Australian Citizenship Act would function as a work-around. The idea was never adopted, for good reason: there was no guarantee that anyone who lost their Australian citizenship in that way would actually be allowed to return to another country.

It is not clear what the expected outcome would be of the 'citizenship solution'. Revoking the Australian citizenship of someone engaged in jihadist activity would deny further access to Australia but would not stop the person from engaging in political violence elsewhere. Only prosecution, conviction and incarceration, whether overseas or in Australia, would achieve that.

Citizenship solutions are always harder in practice than they look.