All the questions you have about Larissa Waters' resignation answered.

She was the first woman to breastfeed in the Australian Senate. She fought to save the Great Barrier Reef from the effects of pollution and global warming. She stood up against cuts to domestic violence services and campaigned for equality for women across Australia.

And now Co-Deputy Leader of the Greens Larissa Waters has resigned from Parliament after discovering that she has dual-citizenship with Canada—a fact that has rendered her ineligible for a seat in the Senate.

Waters is the second Greens senator within the week to resign because of dual-citizenship status.

Fellow Deputy Leader of the Australian Greens (they shared the title) Scott Ludlam announced his resignation on Friday after discovering he shared citizenship with his birthplace, New Zealand.

It is with a heavy heart that I am resigning as Senator for Qld and Co-Deputy Leader of the Australian Greens. https://t.co/DuplaZPi2h

— Larissa Waters (@larissawaters) July 18, 2017

What’s the law?

The Australian Constitution bans dual citizens from being elected to a seat in Federal Parliament. (State parliaments do not have the same restriction.)

The only way a dual citizen can be elected to the Australian Senate or House of Representatives is to show that they’ve taken reasonable steps to sever foreign ties.

This is what former Prime Minister, London-born Tony Abbott, was referencing when he shared a photograph of his UK visa cancellation in the midst of the media storm that followed the two resignations.

FYI rumour mongers: I renounced my UK citizenship in 1993 and here’s the proof: pic.twitter.com/tHAeJeqo5T

— Tony Abbott (@TonyAbbottMHR) July 14, 2017

This step showing that an MP or Senator has taken active measures to shed dual citizenship is where Waters fell down.

The 40-year-old Senator for Queensland moved to Australia from her birthplace in Canada when she was 11 months old. She was “naturalised” to Australia (attained Australian citizenship) and believed she’d renounced her Canadian citizenship by default.

“I thought I had the choice at age 21 to choose whether to be a Canadian citizen,” she told media yesterday. It was something her parents had told her, without knowing that Canadian laws changed soon after their daughter was born.

“I chose not to [apply for Canadian citizenship] but it seems the law was changed a week after I was born and in fact, I should have actively renounced Canadian citizenship,” Waters said.

The law is written under Section 44 of the Australian Constitution, which came into rule in 1901.

Both Waters and Ludlam signed a form on their way to Federal Parliament declaring they had no reason to be disqualified under Section 44. Today both claim that they were unaware of their dual-citizenship when they were elected to office.

“I want to take full responsibility for that. It was an oversight that shouldn’t have happened," Waters told media yesterday. "And had I had no been under the assumption all my life that I was not a Canadian citizen, I would have rectified it at the first opportunity."

Ludlam took a similar tone.

"This is my error, something I should have checked when I first nominated for pre-selection in 2006," he said on Friday. "It never occurred to me as someone who left New Zealand as a 3-year-old, [as someone who] has never really considered it home."

"This town is home. I have been here since 1978. It never crossed my mind that citizenship might be something that sticks to you in that way."

Two great things that happened in Parliament. Post continues below.

The leader of the Greens Party has also issued an apology, with many commentators pointing to the Greens' relatively rapid rise in power—from being a "fringe" party to a major player in Canberra—as one reason some usual checks and balances were overlooked.

“There is no question here—I won’t sugar coat it—we need to make sure that our internal party processes are up to the challenge,” Leader of the Australian Greens Richard Di Natale told reporters yesterday.

“We have to improve our governance. We have to strengthen our internal processes and we have to make sure that this doesn’t happen again."

Is there anyone else who might be affected?

Before the resignations of Waters and Ludlam, 25 people in the current Parliament were known to have been born overseas—and since, many have publicly confirmed their eligibility for a seat.

"I have met my constitutional requirements regarding section 44. To do this, I engaged two teams of lawyers (Australia and Iran) and spent $25k on legal fees (which I paid myself)," Labor Senator Sam Dastyari, who was born in Iran, posted to Facebook yesterday.

"It was difficult, expensive, lengthy and precarious for my family still living in Iran," he added. "Nonetheless, the rules are the rules and I have met them to ensure I meet the requirements to be properly elected."

What happens next?

There is a slight possibility the pair will be required to pay back money they've earned serving in the Australian Senate; however, this is unlikely and hasn't been enforced in previous cases.

Their Senate seats will remain vacant as the case is deferred to the Court of Disputed Returns.

In the meantime, Senators from different parties, including Pauline Hanson of One Nation and Nick Xenophon of SA Best, have warned the Coalition against taking advantage of its temporary advantage in Senate numbers.

“No party should opportunistically abuse the situation while replacements are being chosen,” Xenophon told Guardian Australia.

“If people start abusing the situation as that would set a bad precedent with a long term poisonous effect on the operation of the Senate.”

i'm so proud to have spent six good years on the campaign trail with the exceptional @larissawaters. shine on. pic.twitter.com/AAUKXcRAAu

— Scott Ludlam (@SenatorLudlam) July 18, 2017

Will the law change?

According to the latest census, 28 per cent of Australian citizens were born overseas. This is a growing segment of Australia's diversifying population that is unable to run for federal parliament without spending time and money revoking citizenship.

A referendum would be required to change the law. The last referendum to be carried was held 40 years ago, in 1977.