Abbott flagged plans in February when delivering a national security statement to strip citizenship rights from dual nationals involved in terrorism at home or abroad. The Prime Minister cited the example of Man Haron Monis - the Iranian refugee who became an Australian citizen and carried out the Sydney cafe siege - and warned "people feel like we have been taken for mugs".

Citizenship has to "mean something", Abbott insisted, reciting the pledge that is required for migrants adopting Australian citizenship, but remains optional for people born in the country.

Last week, the government promised amendments to the Australian Citizenship Act, but went beyond dual nationals. Australian nationals could also see suspended "some of the privileges of citizenship for individuals involved in terrorism". Welfare payments are the usual example, as well as passports or voting rights.

So far, the government has balked at stripping citizenship from Australians who have the option to, but haven't yet, become citizens in another country. This is reportedly Abbott's favoured approach.

The government has also released a consultation paper, posing questions and asking for public views on the rights and responsibilities of citizens. The draft legislation is expected to be released in the coming months.

Who would have the power to revoke citizenship, and what right would those who lose it have to appeal?

The law has long held that any dual citizens who join an army at war with Australia will simply forfeit their citizenship. This can also apply to their children. But that law, dating back to the 1940s, envisaged service with an "enemy country", not the transnational nature of modern terrorist groups.

Yet any change immediately raises definitional questions about what, precisely, is a terrorist group, and what qualifies as an act of terrorism? Is it someone who carries a gun in Syria, or a teenager who pledges allegiance to Islamic State from a computer in suburban Melbourne? Abbott spoke of "serious terrorist-related activities". The law is broad.

The Immigration Minister already has scope to revoke citizenship for dual nationals in limited circumstances, where fraud or other crime is committed, such as a fake marriage or payment of a bribe.

This plan appears to concentrate more power with the Minister to make a judgement about terrorists. The government has flagged judicial oversight, but that will be complicated if a person is stripped of citizenship while overseas.

Is there a precedent for these changes - both those announced and those discussed within government?

Australia has accepted an international obligation not to make a person "stateless". Movie fans might remember the character played by Tom Hanks in the 2004 film The Terminal, a man forced to wander for months in an airport while in legal limbo.

The precise definition of statelessness is a person "not considered as a national by any State under the operation of its law". But Britain has adopted a law to strip citizenship from a person who has the option of citizenship elsewhere.

The US, which has never signed the international conventions, also has the option of revoking "naturalised" citizens within a five-year period for serious crimes or dishonourable discharge from the military.

Joining a terrorist organisation can also see an American stripped of their citizenship, but only by a court.

What has been the reaction in Australia and overseas?

Talk of stripping Australians of their sole citizenship has split federal cabinet, but the government has not yet committed to any specific changes. The consultation paper poses broad questions and Abbott has said the idea is to kickstart a broad national conversation about the responsibility of citizenship.

Labor will back moves to update the automatic revocation of citizenship for dual citizens that take up arms against Australia.

But some lawyers are wary and question the need. The Foreign Minister already has the power to revoke passports, and despite all the attention to supposed "jihadi bludgers", the Attorney General's department admitted last week none of Australians suspected of fighting in Syria or Iraq had been on welfare.

There are also warnings the changes will only further alienate the Muslim community. And there is concern Australia would only be foisting terrorists only other countries, rather than taking responsibility for imprisoning them here.

How many stateless people are there in the world, and what is their fate?

The United Nations refugee agency estimates there are at least 10 million people worldwide with no nationality. The Rohingya asylum seekers in south-east Asia are the most prominent example, denied citizenship by Myanmar. About 800,000 people in Myanmar are deemed stateless, the largest population anywhere.

Schooling, work rights, or access to everyday services such as banking are all made far more difficult without an official identity.

But the government insists any changes in Australia to citizenship laws will not add to the global statelessness problem.