What does Monday's decision by the Crown Prosecution Service to drop charges against almost all the protesters – many from UK Uncut – who occupied Fortnum and Mason on the day of the TUC march in March tell us about the state of dissent in the UK today?

First, the reasons given by the CPS tell a tale: continuing with charges against the 109 individuals would not be in the public interest. It was a single incident, those involved had no previous record or were only involved in a very minor way, and the likely sentence if convicted would be a nominal penalty. How has it taken so long for the CPS to realise they should drop charges – and why do so en masse, on one day?

It was clearly a single incident, "as any fule kno", and the likely sentence too would have been predictable from the date they were all arrested some four months ago. If checking previous criminal records has taken since then, there is something drastically wrong with the computer system. That leaves only the extent of any one individual's involvement. Can it really have taken four months to work that out? Or has the desire to send a clear message to sympathisers played a role? We should never underestimate the chilling effect of lingering criminal charges on those who might be tempted to follow the occupiers' example.

This is what is so worrying about the death of Ian Tomlinson, on the less personal and individual level, and about the media portrayal of those who are "kettled". There is a real risk of the criminal justice system being used pour décourager les autres from exercising their democratic rights.

Secondly, the dropping of the charges came only a few days after Charlie Gilmour was sentenced to 16 months for his one-person rampage last December, and a week or so after A-level student Francis Fernie was given 12 months (by the same judge, Nicholas Price QC) for his part in the March protests. Fernie pleaded guilty to throwing two placard sticks at police … and missing. Some say that violent protesters are receiving stiffer sentences than those responsible for run-of-the-mill Saturday night closing-time violence.

Of course, as Judge Price said when sentencing Fernie, the right to protest "is a hallmark of our democratic society … but the rule of law requires that demonstrations are also peaceful. The court does not tolerate violence against anyone and does not condone violence or threats of violence against the police, who are acting in their duty to protect others." Against that though, we must balance how the reading of such sentences – or charges hanging over the Fortnums protesters – are received by the public. Neither Fernie nor Gilmour was innocent and neither was peaceful.

But people do become caught up in violence and the police (some, not all) do respond in the same vein – I personally know of people who were hit with shields in March – and the situation escalates and provokes individuals to act in ways they later regret. If we add to that the obvious disparity between the treatment of Fernie and Gilmour and the leniency shown for years to PC Simon Harwood – who is only now facing charges following Tomlinson's death – all is not necessarily rosy for those wanting to make their views known, and certainly not if you are a black or Asian protester. As research by Joanna Gilmore last year showed, they are much more likely to be arrested and, if convicted, sentenced more severely.

Finally, the decision to drop charges does not explain why the CPS is pursuing its cases against the remaining 30 or so protesters. Aggravated trespass is a strange beast: one of several crimes where the constituent element is trespass, usually only a civil, private matter between (say) the owners of Fortnums and each protester. Indeed, it has only been possible to charge people protesting inside a building since a change in the law in 2004. For the first 10 years of its life, the offence required those charged to be "in open air" – as hunt saboteurs, the obvious targets of the new criminalisation in 1994, would have been. Aggravated trespass is one of a raft of overlapping offences in the armoury of the CPS: an easy option, in many cases.

If there had been violence, then charges of assault would surely have stuck – and been more appropriate? Similarly, if there had been damage to property, would many of us have baulked at prosecutions for criminal damage? From contemporary reports, neither seems to have taken place and if it did, was sporadic and isolated. What we are witnessing, as on many occasions is the past, is the full force of criminal sanction being brought down on those making a point peacefully. We might not agree, we might not like it. But isn't that the point?