Ignorance of the law is, for most of us, no excuse for breaking it. But for the people charged with running our country, breaching the eligibility rules around dual citizenship in our constitution is one of those trifling matters anyone could overlook. Now that the situation, having enveloped six senators and a member of parliament (and implicated many more) has gone past ridiculous, we thought we’d save our politicians a bit of time and list some of the unusual ways the ways one can become a dual national, so they’ve no excuse not to check.

By birth

OK, it might sound obvious, but it’s a fairly small number of countries that observe unrestricted Jus Soli (the law of the soil), which confers citizenship on anyone born in that country regardless of their parents citizenship. Sadly for the Greens, New Zealand used to, and Canada does, snaring Senators Scott Ludlam and Larrissa Waters respectively and setting this whole gory story into motion. Ludlum could have acquired his citizenship a few ways — being born in New Zealand to parents who, also apparently unknowingly, had New Zealand citizenship — while Waters’ three months in Canada (born there to Australian parents) was enough to confer upon her Canadian citizenship.

Apart from that, the United States, most of South America and Central America and a handful of countries in Europe, Africa and the Middle East offer automatic citizenship to children of non-citizens born there. As far as we know, no MPs where born in Pakistan or Antigua.

By descent

This the most commonly racked up by parliamentarians in our current crisis. Italy, New Zealand and the United Kingdom (very generously, or miserly depending on your view, in some cases) all allow people born overseas citizenship through descent — and this has potentially done in Deputy Prime Minister Barnaby Joyce, and Senators Fiona Nash, Matt Canavan, Malcolm Roberts and Nick Xenophon. In the case of Italy, where Canavan has heritage through his grandparents, there is no limit on how far back that descent can stretch, as long as none of your ancestors have previously renounced their citizenship.

In some cases, this can get decidedly fiddly. For example, Sweden confers citizenship automatically to anyone born anywhere in the world to a Swedish mother, regardless of the father’s nationality. If the father is Swedish and the mother is not, a child born outside Sweden will only be a citizen of Sweden if the pair are married. If they are not, the child will not be a Swedish citizen. Unless their parents do decide to marry before the child turns 18, in which case the child will become a Swedish citizen from that date. Latt (Swedish for easy).

By investment

Any MPs looking to invest in the beautiful Islands of the West Indies should think twice — invest generously enough, and you might just acquire a new passport. According to Henley and Partners a citizenship planning firm that caters to wealthy clients: “Citizenship-by-Investment programs offer you the opportunity to legally acquire a new nationality and an alternative or second passport quickly and simply, without major disruption to your life.” Antigua and Barbuda, Grenada, St. Kitts and Nevis all offer such programs, as do Austria, Malta and Cyprus in Europe. 

By role

Vatican City confers citizenship on the Pope, all cardinals residing in Vatican City, active members of the Holy See’s diplomatic service, and other directors of Vatican offices and services, as well as any spouses or children of those who hold citizenship by office, so long as they are also residents. While dual citizenship of the Vatican city state is technically possible, Vatican citizenship expires when the role does, making it pretty tough for an MP fall afoul of the constitution this way.