Tuesday's NEC meeting saw the Labour Party adopt new rules to restrict participation in its leadership contest. Presumably their intent was to assist anti-Corbyn forces by limiting the size of the pro-Crobyn selectorate.

But in doing so the NEC has made a fundamental strategic miscalculation. It has chosen to refight the leadership contest of summer 2015 instead of setting the stage anew for summer 2016.

To understand this, let's first consider what the big changes actually are:

a freeze date of six months (meaning members who have joined since January can't vote in the leadership contest)

an increase in the supporter registration fee from £3 to £25

a registration window of just 48hrs from Monday for new supporters

affiliate registration deadline of August 8 (meaning that you can join a trade union or socialist society like the Fabians and vote in the leadership contest)

Anti-Corbyn forces hope that these restrictions will prevent the participation of the near 150,000 new members that the Labour Party has added since 23 June alone.

This has presumably been done because the experience of last summer was that Corbyn won the full membership more narrowly then the registered supporters section, which he won overwhelmingly. Thus restricting these supporters makes for a closer race among members.

But such a logic, however undemocratic it may be, only holds if those new members are not able to find an alternative route into the franchise. Yet this is precisely what the affiliates route offers. As a consequence recently disenfranchised members can rejoin the leadership race by registering as an affiliate voter. Expect Unite to expand on its low cost membership scheme to allow exactly this to occur on a large scale.

In attempting to restrict voting but leaving the affiliates route open, the NEC has thus made it easier to recruit through affiliates and harder to do so without them.

In essence, this means new voters face higher barriers to entry. But the pro-Corbyn faction have significant numbers of voters who are probably willing to endure high barriers for their cause.

In contrast, the anti-Corbyn faction may have a larger potential pool of voters, but these voters are likely to be deterred by high barriers to entry. Previously, the message could simply have been: "Angry about Corbyn's role in Brexit? Join Labour today." Now this faction will have to say: "Angry about Corbyn's role in Brexit? Join a trade union you may dislike or a socialist society you've never heard of."

Pro-Corbyn supporters who have joined since January have both a strong pull factor (Corbyn) and a strong push factor (disenfranchisement). What's more, their politics likely align with that of the Unite leadership, which offers them an easy, low cost means of voting in the contest.

Anti-Corbyn forces are now trying to shut the barn door after the horse has bolted by attempting to impose a freeze date on affiliates. But enforcing such a rule on affiliates may prove difficult.

Last summer Labour was consumed by the mass participation of pro-Corbyn supporters. His opponents could have responded by beefing up their own numbers through mass recruitment at as low an entry cost as possible. Such party might have actually reflected the Labour electorate at large.

But rather than out-recruiting the Corbynistas, the anti-Corbyn forces tried to win this fight using the rule book. Unfortunately for them, in leaving the affiliates door open, they may well have outsmarted themselves.