28/07/2017 3:23 PM AEST | Updated 29/07/2017 6:25 AM AEST

Why Can't You Be An MP If You're A Dual Citizen?

It goes back to a British law from the 1700s.

Two Greens senators have resigned. One government minister has had to step down from his portfolio. There are serious questions being raised over a One Nation senator and another government MP, and a reported 20 more hurriedly checking their paperwork. Section 44 of the Australian constitution is smashing through the federal parliament like a wrecking ball, as parliamentarians sweat over their citizenship and whether they -- knowingly or not -- hold some foreign citizenship status.

But why can't you be an MP if you're a dual citizen? The section of the constitution in question, 44(i), states:

Any person who: is under any acknowledgment of allegiance, obedience, or adherence to a foreign power, or is a subject or a citizen or entitled to the rights or privileges of a subject or a citizen of a foreign power... shall be incapable of being chosen or of sitting as a senator or a member of the House of Representatives.

Australia is today one of the most successful multicultural countries in the world, with the 2016 census reporting 49 percent of all Australians were either born overseas or had at least one parent who was born -- as we've seen in the cases of Scott Ludlam, Larissa Waters, Matt Canavan, and now in recent days Malcolm Roberts and Julia Banks, this overseas connection means many millions of Australians may hold or be entitled to foreign citizenship. Why are so many Australians essentially barred from parliament?

It comes down to an old English law from the 1700s, according to Professor Anne Twomey, a constitutional law expert and director of the Constitutional Reform Unit at the University of Sydney Law School. She told HuffPost Australia it linked back to the Act of Settlement from 1701, which has tendrils snaking all the way to today.

"It says only people who are born in England, Ireland, Scotland and the dominions, or of English parents, can be members of parliament. When the British set up Australia and the colonial legislatures, the 1842 acts they enacted in the NSW legislative council, it uses similar terminology to the 1701 act," she said.

"The Act of Settlement came out of conflicts, religious conflicts. Treason was essentially the concern at the time. Yes the world is different now but no we haven't changed the terminology since 1701. The reason it hasn't been changed is because the underlying principle that you should have sole allegiance to the country you want to represent, that still has resonance. Should you have a right to bail out and go somewhere else?"

Section 44 is just 267 words long, with five sub-sections, but in the current 45th parliament alone, it has claimed the seats of four senators with the potential for a few more -- Waters and Ludlam under 44(i) relating to citizenship, Rod Culleton under 44(iii) relating to someone classified as an "undischarged bankrupt of insolvent," and Bob Day under 44(iv) relating to someone who "holds any office of profit under the Crown". It is the citizenship provisions which are currently under the spotlight, with Nine News reporting more than 20 MPs may come under scrutiny.

"The argument is, if you're holding an important position and making decisions, your allegiance should be to Australia. The argument is [if you're a dual citizen] you might be influenced by your other country and other interests. You have to ask yourself, what's the cost of giving up their dual allegiance, if all you have to do is sign a letter to the embassy. Whats the cost to that? Is that really impeding people from being a MP?" Twomey said.

"If you're that committed to Australia, you should be happy to give up your ability to get through the quick line at Heathrow airport. The difficulties arising lately are due to people not doing due diligence to check if they had dual citizenship. You'd find they would be happy to give up the dual citizenship, that's not the problem, it's that they didn't check before becoming an MP."

While there have been calls in recent weeks for section 44(i) to be removed or its definition to be loosened -- considering Ludlam, Waters and Canavan had no idea of their dual citizenship status, and therefore, it would be a long bow to draw to say they had any "allegiance" to those countries -- Twomey said it was unlikely to be changed anytime soon. For one, it would require a referendum on an issue only affecting 226 people in the entire country. For another, the professor said the current laws aren't really an impediment.

"I don't know how a referendum on that would play out, but it's not such a big deal or problem for people to risk their political capital and money to run a referendum like that. The problems not are because people aren't finding out and not doing due diligence," she said.

"Lot of bodies have been saying we should get rid of that provision, particularly at height of multiculturalism. All those concerns revolved around problem of people who come from countries where you cant renounce your citizenship. But there was the Sykes vs Cleary case of 1992, where the High Court ruled that, so long as you've made reasonable efforts to renounce that citizenship, that's enough."

Politicians nationwide are scurrying to confirm their citizenship status and ensure they are not unwittingly a dual citizen of Australia and a second country. On Friday alone, One Nation's Malcolm Roberts threw more fuel on the fire of speculation around his possible British citizenship, while it was revealed that Liberal MP Julia Banks may hold Greek citizenship.