Never before in the UK has the membership of a political party wielded so much direct power over the programme of a government.

On Saturday, an extraordinary general meeting of the Scottish Green Party will debate whether to accept an offer from the SNP, which would see Green MSPs appointed as government ministers and a long list of the party’s policies adopted. Any member will be entitled to attend, and to decide.

If the proposed deal is supported by the membership, it will then have to be signed off by the party’s council, with representatives of each local area, internal party group and committee.

Should two-thirds of this council agree, then, and only then, will the SNP’s deal with the Greens – already treated by much of the media as though it’s confirmed – be passed.

I should confess an interest. I’ve been a member of the Scottish Greens since 2001 and have the right to vote at that EGM. I used to sit, on and off, on that council and was vaguely involved in designing the process that would be required to sign off any such agreement, many years ago.

There is a huge amount of great stuff in the deal. As others have said, it looks to meet many of the demands long fought for by activist groups and social movements in Scotland: rent controls to put a lid on the housing crisis, reform of the Gender Recognition Act to make it easier for trans people to be legally accepted for who they are, a ban on conversion therapy. My own family WhatsApp group vibrated with debate about the specific promises on reintroduced beavers, for which our mum has long led the campaign.

If it’s passed, public contracts will become conditional on companies paying their workers a living wage, giving them a voice through trade unions, and not dodging tax.

On-shore wind capacity will double, billions will be invested in the railway network, on top of the SNP’s existing promise to renationalise, infrastructure for cycling and walking will get a boost, all new homes will have carbon-neutral heating. The wide array of proposals have been welcomed by campaign groups from Friends of the Earth Scotland to Shelter to Living Rent, Scotland’s tenant’s union.

Ultimately the plan aims to bring together Scotland’s two main pro-independence parties to deliver a referendum on escaping from Westminster rule. There has been something delightful about watching dark patches seep through newspapers across the UK, as right-wing commentators wet themselves at the very prospect, as well as the disgust at realising some have smeared themselves in homophobia.

Should Scottish Green members fail to back the pact, then the SNP would continue to hold power in a minority government. In that case, it’s not clear whether the party would stick to any of these policies, and it may look to its right to get its budgets and bills through. However, supporting the deal brings with it huge risks.

As I wrote before the deal was published, I don’t see how Greens can take part in a government that fails to do all it can to block the exploration for and extraction of new oil and gas reserves from the seas around Scotland. Selling North Sea oil is by far the country’s biggest climate impact, and while energy-efficient homes and renewably powered electric trains will be a wonderful contribution to inventing a zero-carbon future, they’ll be little more than signal-buoys floating on a sea of crude.

The Scottish government doesn’t have any formal power to grant licences for pumping from the North Sea bed – that’s down to Westminster. But it can choose to block planning applications for most of the requisite onshore infrastructure. And, given that the world is on fire, it should.

Unfortunately, the urgency of the situation is met with hesitation. Research is promised, by the end of 2022, so the government can “take an informed policy decision on the contribution of North Sea production to the global climate emergency”.

We don’t need a year and a half to establish that burning oil heats the planet. We’ve known that for more than 100 years.

Promises to deliver £500m for a ‘just transition fund’ for oil workers are wonderful to see, but unless there is a firm commitment that will mean a rapid transition away from oil and gas extraction, they will scarcely matter to the people whose lives and livelihoods rely on averting the worst of global heating.

Similarly, the deal comes as the UK emerges (hopefully) from the pandemic, and into another huge debate over public spending. Some 72% of the Scottish government’s income comes from Westminster, and it seems almost inevitable that this will be slashed as chancellor Rishi Sunak tries to dig his way out of the debt-hole left by COVID.

There is only a limited amount that the Scottish parliament, with its restricted powers, can do about this. But there is little sign in the deal that the SNP-led government will do even that. There’s no suggestion that tax powers will be used, for example, to ensure the most pain falls on the richest Scots. For the Greens, entering a government just as it’s likely to have its budget slashed is a huge political risk. And it’s worth asking, what’s the SNP risking in exchange? What is it promising that it really doesn’t want to do? What has it ditched that it is keen on?

The answer, it seems to me, is, not very much. The SNP’s manifesto in May was thin on policy, and most of what they’ve taken from the Greens are good ideas, many of which they might well wish they’d had. Beyond rent controls and tenants’ rights, few of the proposed ideas mean picking real fights with people with much power.

That, though, was only the first stage of this process. The SNP may enjoy announcing decisions made by leaders from podiums – the party is so shaped by a decade and a half of governing in a system modelled on Westminster that that’s how it expects things to be done.

But in the Greens, members have real power. And for party activists deciding whether to accept or reject this deal, it’s therefore worth asking a third question. Can they use this power to lever anything more? It’s perfectly normal for a negotiating team to go back to their board, or members, or colleagues, and be told they have to go further. There’s nothing wrong with a group of representatives being given a firm mandate to push harder.

So far, this conversation has taken place on the SNP’s home turf, in the legalese of civil servicedom. But if Scottish Greens have strength, it lies in their growing position as a party of Scotland’s social movements, and it’s time for them to use that might. Much of the media will, of course, laugh at the chaos of ordinary people setting the agenda. But that’s because they are afraid that real democracy leaves them naked.

Never before in the UK has the membership of a political party had so much direct power over the programme of a government. Let’s hope they use it.