This afternoon Greens senator Scott Ludlam announced his surprise resignation from federal parliament.

Ludlam resigned after it was brought to his attention that his New Zealand dual citizenship meant he was ineligible to sit in parliament. It’s all happened very quickly, so let’s take a look at what’s actually going on and what this means for Ludlam and Australian politics.

Why Did Scott Ludlam Resign?

Section 44 of Australia’s constitution states that 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” is ineligible to sit in federal parliament. Basically, if you’re a citizen of any other country you can’t be an MP — even if you hold Australian citizenship.

Candidates who were born overseas or have dual citizenship have to renounce their citizenship of another country before they run.

Ludlam was born in New Zealand and moved out of the country when he was three, but as we found out today he never renounced his New Zealand citizenship. That means that he is ineligible to serve as a senator.

Rather than waiting for someone to challenge his legitimacy in the courts, Ludlam decided to resign soon after being alerted to his slip up by a member of the public.

Does That Mean He Was Never Technically A Senator?

Well, yeah. Pretty much. Because Ludlam never renounced his citizenship he was technically ineligible when he was elected in 2007. And 2013. And 2014. And 2016.

So what does that mean when it comes to all of the important bits of legislation he voted on? That’s still unclear. The Greens said they had legal advice suggesting that Ludlam’s resignation wouldn’t somehow invalidate his votes. But if someone wanted too they could take the whole thing to the High Court and get them to rule on the validity of Ludlam’s entire political career.

Who’s Going To Replace Him?

Now that Ludlam has resigned, the Court of Disputed Returns needs to decide what the process is from here. The most likely outcome is a re-count, which will probably lead to a the third candidate on the Greens WA Senate ticket being elected.

That candidate is a 22 year old called Jordan Steele-John. Steele-John, who has cerebral palsy, works in disability advocacy. He’s previously run for the Greens in the seat of Fremantle.

Could Ludlam Make A Political Comeback?

There’s nothing stopping Ludlam from renouncing his New Zealand citizenship and running for parliament again. In fact, if Steele-John becomes a Greens senator, he could then resign, triggering a casual vacancy. That vacancy would then be filled by a nominee of the Greens, which could be Ludlam.

But Ludlam was pretty quick to dismiss suggestions he was looking at a comeback today. In his statement today he said “I’ve been incredibly fortunate to serve these past nine years in the Australian Senate.

“I’ll find a way to continue making a contribution in some different capacity, but thank you all for sharing this remarkable ride with me.”