Citizenship stripping also undermines our collective responsibility as a national community. Denationalisation is a modern form of banishment – a process of collectively washing our hands of an individual member and making him/her another state's problem. Denationalisation is thus open to the same criticism that Voltaire made of the practice in 18th century France: namely, that it simply constitutes throwing into our neighbour's yard those stones that incommode us in our own.

The home-grown terrorist is by definition the product of our society, albeit a deviant one. To banish him/her to another state—typically a weak and conflict-ridden one—is to abdicate our own responsibility as Australians for our own creations, as well as to act unjustly towards the states that must now take them in. Denationalisation may also encourage us to overlook the features of our society that might have made them dangerous individuals in the first place.

A final concern is that denationalisation will pierce a small hole in the security of citizenship that will grow over time. This has been evident in Britain's experience with denationalisation power. When denationalisation power was revived by the Blair government in 2002, it was tightly constrained and subject to judicial appeal. Only a handful of people lost their citizenship. But after the London bombings in July 2005, the bar necessary for denationalisation was dramatically lowered. The British government now had only to be satisfied that taking away someone's citizenship was "conducive to the public good" to justify citizenship loss.

This change led to growing use of the power. In the first four years of the Cameron government, more than 23 people were stripped of citizenship. Almost all of these individuals lost their citizenship while outside Britain , undermining their access to appeal procedures. Last year the Cameron government expanded its powers further. Under current law, the British government can strip citizenship from naturalised citizens even if they would be made stateless. A small change to British citizenship law in 2002 has led to a situation where British nationals now hold the least secure citizenship of any Western country.

There is no doubt that some Australians are not good citizens and arguably some do not deserve to hold Australian citizenship at all. But we need to separate out this observation from the question of what is the appropriate response to Australian terrorists. By endorsing the Abbott government's proposal to strip citizenship from bad citizens, we risk undermining the key values – equality, responsibility, and security of status – that make our citizenship worth holding in the first place.