John McTernan: A thick skin, not the courtroom, is the best protection in the rough and tumble of politics

All's fair in love and war, but not apparently in elections. The verdict that has barred Phil Woolas from holding office as an MP for Oldham East and Saddleworth has sent a chill down the spine of campaigners across the country. Suddenly new standards of veracity are going to apply to political discourse. You could almost hear the shredders whirring into action as leaflets were being dumped.

This is a serious business. The anger expressed by Labour MPs on Monday at the weekly meeting of the parliamentary Labour Party (PLP) partly reflected their respect for Mr Woolas, who is a good and decent man. But it also revealed a genuine fear – a concern that the laws of politics were shifting, and under their very feet.

And I agree, politics is a contact sport – if you don't like a bump or a bruise, try something more gentle like flower arranging. Bringing in the law to adjudicate on the truth (or otherwise) of political statements is a game changer – and a real danger. What would the courts make of Macmillan's claim "you've never had it so good" or Wilson's statement in the sixties that devaluation didn't affect the "pound in your pocket."

Famously, the novelist Evelyn Waugh was trying to leave a building as the essayist GK Chesteron was entering. Both were large gentlemen. "Sir, I never give way to a fat fool", said Waugh. "Sir, I always do", responded Chesterton. A brilliant riposte, yet illegitimate according to the logic of the court that found Woolas guilty. Precisely how fat? And according to which community standard a fool.

This is, of course, the easy end of the problem. How far can you go with a colourful assertion or insult. A more disruptive thought is – how far does this question of truth go? Lib Dem MPs signed up to a pledge not to raise tuition fees – should they be debarred as "liars" because they vote for a different policy. David Cameron promised no top-down reorganisation of the NHS, yet he is about to embark on what his health minister for England describes as the most radical reform of the health service since Bevan.

Should Cameron be barred from his seat? Or the Lib Dems thrown out of the Commons when they vote for a scheme that trebles tuition fees? Of course not. It's in the game. But then these unelected judges choose to mix it. What if we, in the political world, started telling them how to do their job? To the frustration of successive governments, judges have increasingly intervened in the political process – ruling restrictions on controversial issues such as immigration or terrorism unlawful.

The Woolas case suggests the law wants to go far further. If what a politician says in an election campaign can be judged true or false then where do party's manifestos stand? It's an utterly absurd idea that policy promises should be legally enforceable. And as for insults – surely "sticks and stones my break my bones..." Is the right attitude. Not, where's my lawyer...