Labour's attack on Reform is straight out of the Trump playbook

There are plenty of reasons why you might dislike the two huge donations announced by Reform UK over the weekend. Perhaps you fear the prospect of American-level funding in British politics. Maybe you’re concerned about money buying influence in the corridors of power. Alternatively, you might have an aversion to crypto billionaires. Maybe you just oppose Nigel Farage and his party. Or, most likely, it could be some combination of all four.

Each is a perfectly legitimate position to hold, though I suspect that the Government’s outrage about the news is more heavily weighted to the last factor on my list.

For ministers battling Reform’s threat to seize Labour’s voters, its seats and its grip on power, the prospect of Farage sitting on a £72m war chest from two cryptocurrency billionaires is more than a little alarming. That the Prime Minister abandoned his previous support for a cap on donations three weeks ago, amid concerns that it might affect his own party’s funding from the trade unions, doesn’t help.

However, a solution has presented itself: while the Government isn’t capping donations generally, it has already announced plans to cap the money given by British citizens living abroad – a cap which would apply until they have been back in the country for more than 12 months.

The law hasn’t been changed yet, but Housing Secretary Angela Rayner suggested on Sunday that once introduced, it would apply retrospectively. She was so keen on this news that she returned to it several times, because the Government evidently believes that this would invalidate these Reform donations, even though they have already happened. Flash! And the cash is gone…

It’s easy to see why this might appeal to Labour ministers. It might also appeal to anyone concerned about the donations for all the reasons I listed above. But it is deeply troubling, nonetheless.

A fundamental principle of British law is that it should not be retroactive. Parliamentary sovereignty means Parliament can legislate for whatever it might wish – it could legislate that the moon is green – but we have long-established conventions which govern how that power ought to be used. One of those conventions is that retroactivity is bad and should only ever be used in rare circumstances.

This exists for good reason: when you decide how to conduct yourself today, you will – as a good, well-informed and law-abiding citizen – make those decisions in part based on whether they are legal or illegal. A future government is entitled to come along later and make such decisions illegal from that point onwards, meaning you can no longer, say, drive without a seat belt or smoke in a pub. But it would be manifestly unjust for it to reach back into the past and turn those who already did things that were legal at the time into law-breakers.

This convention is particularly strong with regard to criminal law, because the penalties involved are all the more serious. Life in a world in which you might one day be sanctioned or even imprisoned for doing something that was legal when you did it would rapidly become impossible.

The Political Parties, Elections and Referendums Act (PPERA), the legislation which governs political donations, is indeed criminal law, with penalties rising through fines to imprisonment falling within its remit.

While Rayner told the BBC that Ben Delo and Christopher Harborne’s donations would simply be required to be returned, the principle still stands: if it’s legal today, a new law might make it illegal tomorrow – but it should not be able to retrospectively forbid something allowed at the time it was done.

That principle is a general one, but there are also specific reasons why this particular action is unwise. For starters, it appears nakedly political – for the good reason that it is nakedly political – and has instantly become further fuel for Farage’s argument that the establishment will play dirty to stop Reform’s insurgency.

It also opens the door to tit-for-tat use of Parliament’s powers to get one over on one’s political opponents. We may not want to import American campaigning budgets into this country, but we definitely should not want to import the Yankee habit of using every trick to bend the democratic process for partisan advantage.

For example, using electoral boundary reviews to contort constituencies into whatever weird shape is most convenient for polling day is now common in the US – we should do everything we can to keep the election rulebook sacrosanct and above self-interest.

As it is, this gives off uncomfortably Trumpish vibes: the other side is the enemy, they must not win, and that is sufficient justification to stop at nothing and override even long-standing, well-considered conventions to get at them.

When a government gets tempted to push the boundaries of the powers available to it, and to bend convention to get its way, it should have sufficient imagination to consider how this might be used by a government of another colour.

In the great Tudor drama A Man for All Seasons, when criticised for giving “the devil the benefit of the law”, Thomas More replies with one of the finest justifications of the rule of law: “When the last law was down, and the Devil turned ’round on you, where would you hide?… Yes, I’d give the Devil benefit of law, for my own safety’s sake.”

I’m sure that today’s ministers are assured that they would only use this studs-up approach in moderation, or at least that they are only using it against people they consider to be baddies. They should pause to wonder how they would feel if a Reform government, similarly convinced of its own rightness, did the same. They are handing them a precedent to do so.