A very big week is in store for the government’s strategy to tackle illegal immigration with all eyes on the planned first air transfer of irregular migrants to Rwanda, due to take place on Tuesday.

Whether the flight takes off at all and how many migrants will be on board is yet to be seen. But the policy has already attracted strong adverse commentary from leading lights in Britain’s unelected establishment, from the Archbishop of Canterbury to the heir to the throne.

But another struggle over the enforcement of immigration law is being waged at ground level, with the springing up of networks of local activists seeking to prevent immigration enforcement officers accompanied by the police from detaining illegal immigrants to facilitate their deportation.

Only occasionally do the activities of this ‘anti-raids’ movement hit the headlines. In May of last year, two men from India were released from the back of a police van in Glasgow after a large crowd assembled to prevent the vehicle from driving away. As the Guardian later reported, the protesters were summoned to the scene by a group called the No Evictions Network.

Scotland’s First Minister, Nicola Sturgeon, the MSP for the constituency involved, was naturally outraged. But not by the rabble who acted to prevent due enforcement of the law.  No, her beef was squarely with the immigration officers and the police, who she accused of having created ‘a dangerous and unacceptable situation’.

This weekend something very similar occurred in Peckham, south-east London. When immigration officers and later the police arrived outside a property on a local estate seeking to detain its occupant, anti-raids groups went into overdrive, using social media to summon 200 people to the scene to hem in the Border Force van.

Again, the tactic worked, with the intended detainee being allowed to leave the van as the crowd chanted ‘shame on you’ and ‘let him go’ and police officers sought to calm an increasingly fraught situation.

Once more a left-wing elected politician got involved in the effort to thwart due enforcement of the law. This time it was local Labour councillor Reginald Popoola, who helped summon people to the scene by tweeting: ‘Block the van from taking one of our neighbours. Come and join us now.’

Later he posted a celebratory tweet declaring: ‘Here’s the moment he was released from the immigration van. Really proud of our community for turning out today and resisting. Peckham people power!’

It will be instructive to see what stance the former Director of Public Prosecutions Sir Keir Starmer – now a semi-obscure political figure – takes towards a Labour councillor wilfully obstructing the legal authorities in this way and then celebrating their defeat. But as a stickler for due process, one must hope that he will see the merits of the rule of law over ‘Peckham people power’, which seems like a polite way of describing mob rule.

At least a spokesman for the Home Office was clear about the rights and wrongs of the episode, saying: ‘The Government is tackling illegal immigration and the harm it causes, often to the most vulnerable people, by removing those with no right to be in the UK. The operation in Southwark was conducted in relation to suspected immigration offences. Preventing immigration enforcement teams from doing their job is unacceptable. Blocking or obstructing them will not deter them from undertaking the duties that the public rightly expect them to carry out.’

This is all very well in theory. But the awkward fact is that in practice the forces of law and order were deterred, prevented even, from undertaking the duties the public expects of them. Will the bailed gentlemen actually be detained and deported? Will he even be at the address when the authorities return to it? This seems unlikely.

No wonder London’s anti-raids social media groups are cock-a-hoop at their latest street-level victory, with Lewisham Anti-Raids tweeting: ‘After 4 hours of resistance and a crowd of 200 people they’re letting our neighbour go! People power wins. We’re shouting “don’t come back to Peckham!”’

This is all best seen as part of a wider picture of law enforcement buckling in the face of groups that wish to pick and choose which legal constraints to honour and which to feel free to ignore. Last week militant Muslims further enforced the de facto Islamic blasphemy law they have created in the UK by getting a controversial film pulled. Meanwhile a schoolteacher from Batley who dared display a picture of the prophet Mohammed to his class last year remains in hiding.

We have also seen a recent series of court cases heard by big city juries in which left-wing defendants have been acquitted, even though conduct of a criminal nature clearly took place. These range from statue-topplers to climate activists holding up a tube train. The jurors in those cases were of course entitled to reach whatever verdict they considered to best represent justice.

But in a democracy, political causes are best pursued via lawful and democratic means. Instead, we appear to be in danger of sleepwalking into a balkanised Britain, where members of particular identity- and ideology-based groups are able to reject an overarching legal-social contract.

The evidence of recent days suggests that the government lacks the knowhow to get the better of such groups, while more worryingly still, the opposition contains people who are cheering them on.