Chris Ratcliffe / AFP / Getty Images On Tuesday, Labour's ruling national executive committee (NEC) made a series of critical decisions on how the party's leadership contest will operate.The contest is the result of a bitter row between leader Jeremy Corbyn and more than 170 of his MPs who want him out. Because Corbyn has refused to resign, two MPs – Angela Eagle and Owen Smith – have challenged him for the leadership.The NEC ruled that as the incumbent, Corbyn, unlike his challengers, doesn't need to get nominations from MPs or MEPs to be on the ballot – a big victory for him, as it was doubtful he has enough support. But the NEC also introduced restrictions on who will get to vote in the election. So how exactly will it work? Labour party members get a vote, unless they joined recently. Justin Tallis / AFP / Getty Images The most controversial decision made by the NEC was to exclude any members who joined Labour after January 2016 from voting in the Labour leadership election.The move came as a surprise to more than 120,000 people who had signed up to the party following the EU referendum, many of them to support Corbyn in any leadership contest which follows. The restriction has been seen as a stitch-up to exclude them – especially as Corbyn left the NEC meeting before the crucial vote, to address supporters at a rally outside party HQ.Some suggested the "surprise" vote had deliberately been held after Corbyn left. The meeting had, however, been expected in advance to discuss the "freeze date" for membership – the New Statesman's George Eaton had reported this on Monday, and a Labour NEC member had publicly canvassed for members' opinions a day before the meeting.Some new members wish to challenge the decision, as Labour's sign-up website says members can vote for leader, but Labour's rulebook gives the NEC the power to set the freeze date – subject to approval by an independent election scrutineer – and the website's terms and conditions state full rules are in the party rulebook. People can pay £25 to become a "registered supporter" and vote – but only if they do so next week. Ben Pruchnie / Getty Images New rules brought in by Ed Miliband require "registered supporters" to be able to vote in Labour leadership elections – but they also let the NEC decide what the rules covering these supporters are.In 2015's election, registered supporters paid just £3 to sign up, and had a period of several weeks to do so. This time, the rules are much tighter. Registration is only open between 18 and 20 July (next Monday to Wednesday), and will cost £25.BuzzFeed News understands members who joined after January – and who therefore don't get a vote – *are* allowed to sign up as registered supporters and vote that way.Registered supporter status is not party membership. There's no right to attend members' meetings, and it only lasts for the duration of the leadership challenge. Anyone who paid £3 to vote last time does not automatically have a vote this time.You can't become a registered supporter if you're a member or an activist for another political party, or if you've publicly attacked Labour – you have to sign up saying you subscribe to the values of the party.It's because the rulebook requires this status to exist that Labour has the strange situation of barring recent members from the poll, but then opening a new way to sign up. Members of most unions get a vote in the leadership election. Carl Court / AFP / Getty Images Most major unions are affiliated to the Labour party, which means their members can vote provided they haven't opted out of the "political levy" and have registered as an affiliate supporter of the Labour party.Unions are responsible for providing the Labour party with a list of their eligible members for the vote by noon on 8 August – a much later cut-off than for registered supporter status.This is a route many Corbyn supporters are seizing upon as a possibly cheaper way to secure a vote in the Labour leadership campaign.The main way being proposed is "Unite Community" membership: a scheme introduced in 2012 to allow unwaged people like students, carers, and unemployed people to join a union. This membership costs 50p per week, billed either monthly (£2.17) or annually (£26). If cancelled quickly after the leadership contest, this is the cheapest way to vote in the contest.To get a vote, it's not enough just to sign up as a Unite Community member. After sign-up, members then need to do an extra sign-on supporting the aims of the Labour party. They must also be on the electoral roll at the same address as they signed up with to the union.However, people who sign up to join a union now are not guaranteed a vote. The NEC's procedures committee has recommended the same six-month "freeze day" for affiliates as for full members, meaning new signups would not get to vote. This decision, BuzzFeed News understands, will need confirmation at the next full NEC meeting. Members of some groups affiliated to Labour get a vote. Jack Taylor / Getty Images There are multiple groups affiliated to Labour whose members – like trade unionists – get an affiliate vote in the leadership election. Two of the most significant are BAME Labour, which is open to people of black and minority ethnicity who support Labour's aims and costs £5 for two years, and LGBT Labour, which is open to LGBT people who supporter Labour's aims but also has a "supporting members" status for straight people. LGBT Labour membership costs £8 a year.BuzzFeed News has asked LGBT Labour whether these supporting members would get leadership votes, and will update this piece when we get a response.The cut-off for these groups to send their lists to the Labour party for the election is 8 August.It's important to note these organisations tend to be much smaller than unions and so may struggle to process large floods of applications in tight deadlines, if overwhelmed. Some groups have reportedly already closed their door to new members seeking to join to influence the contest: Sunny Hundal @sunny_hundal Scientists for Labour temp. suspend new membership looking to "hijack the Labour leadership election" /ht @leobarasi Wed Jul 13 11:34:37 UTC+0000 2016 Reply Retweet Favorite However, people who sign up to join affiliated organisations now are not guaranteed a vote. The NEC's procedures committee has recommended the same six-month "freeze day" for affiliates as for full members, meaning new signups would not get to vote. This decision, BuzzFeed News understands, will need confirmation at the next full NEC meeting. Can I sign up in all these different categories and get multiple votes? Niklas Halle'n / AFP / Getty Images No – you can't.Simply put, the highest level of membership you have is the one that counts. Full membership trumps being an affiliate supporter, which trumps being a registered supporter. You get a maximum of one vote through whichever the highest status you have is. Trying to get more may get you thrown out entirely. How long is all of this going to go on for? Jim Watson / AFP / Getty Images Until 24 September. Yes, there's another 10 weeks of this.MPs and MEPs can officially nominate candidates to appear on the ballot against Corbyn until 20 July. After this, any challengers who got 51 or more nominations will appear on the ballot for members and supporters. Voting will take place from late August until 21 September.Labour leadership contests are many things, but they aren't fast. If Jeremy Corbyn wins, will Labour just keep having new leadership contests? Jack Taylor / Getty Images This is what MPs are threatening. It's unprecedented for a modern party leader to try to keep in his role without the support of a considerable majority of his MPs – which is generally seen as an essential requirement. Welcome to the new politics.This has led some MPs to threaten that they'll just keep launching leadership contests until Corbyn loses one, paralysing the party. MPs would certainly be able to launch new challenges, but the party's rules appear to suggest that without a vacancy – in other words, while there is a serving leader – these challenges can only be annual. Which would give Corbyn at least a few months breathing space, if he wins.