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Legal case

When to practice caution or prosecution? We delve into the case of protestors on a highway and the rights of police when it comes to arrests.

Director of Public Prosecutions v Ziegler and Others

The Supreme Court offers guidance on the compatibility of an individual being prosecuted for an offence contrary to s.137 of the Highways Act 1980 (‘a s.137 offence’) having blocked a highway with their rights to freedom of expression and freedom of assembly under articles 10 and 11 of the European Convention of Human Rights. In this article we assess the impact of this case on the policing of static or slow marching protests.

Executive summary

Following a finding that the blockage of one side of an access road to the Excel Centre for a period of 90-100 minutes did not cause significant disruption to either the Centre or other members of the public, the Supreme Court found that convicting the protestors with a s.137 offence was incompatible with their article 10 and 11 rights. The Supreme Court offered guidance on assessing the reasonableness of convicting protesters with a s.137 offence. However, given the essential difference between the tests for arrest and prosecution, the case is unlikely to cause any significant shift in the way static or slow marching protests are approached by police.


On 5 September 2017, four protesters took part in a demonstration against the upcoming biennial Defence and Security International (‘DSEI’) fair at the Excel Centre, located in a commercial area of East London.

The protesters lay across one side of the primary approach road to the Excel Centre and locked themselves to a bar in the middle of a box that was designed to make their removal difficult. The other side of the highway was unaffected and notably there were alternative routes available to the Excel Centre. The protesters had given prior notice of their plans to the police, who were present in anticipation of the protest. Having unsuccessfully undertaken the “5 stage process” to persuade them to leave voluntarily, police arrested the protesters for a s.137 offence within minutes of their arrival, although it took a period of 90-100 minutes to remove them and the blockage from the highway.

The protesters were acquitted at trial on the premise they had a “lawful authority or excuse” defence contained in s.137. The acquittal was successfully appealed by the Director for Public Prosecutions, with the appellants thereafter appealing that decision to the Supreme Court.

Decision of the Supreme Court

The Supreme Court decided that on the above facts the protesters had a lawful excuse to block the highway in the exercise of their article 10 and 11 rights. They accordingly had not committed a s.137 offence and their convictions were overturned.

In reaching this decision, the Supreme Court had particular regard to the fact that only one side of the highway was blocked; there were alternative routes to the Excel Centre; the highway was in a commercial area and there was no evidence at trial of any impact on traffic travelling elsewhere than the Excel Centre; and the duration of the blockage was limited to 90-100 minutes.


In considering the implications of the judgment, one must distinguish between the assessment of proportionality of arrest with the assessment of proportionality of charging, prosecuting and convicting a suspect. It is important to observe that whilst the Supreme Court found that convicting the suspects with an offence was disproportionate, no comment was given on whether the initial arrests were disproportionate and/or unlawful.

It accordingly appears that the impact on how protests are policed is unlikely to be affected by this judgment.

This does not mean to say that an officer need not exercise caution in considering arrest. They ought to have in mind whether the suspect has a reasonable excuse for blocking the highway or not, as the fact that a protest is causing more than de minimis disruption will not on its own provide reasonable grounds for an arrest. The officer will need to have regard to the wider circumstances, insofar as they are known, to make their own assessment of the reasonableness of the obstruction.

There is no black and white test for the assessment of the reasonableness of a protest (and therefore the proportionality of interfering with the protesters’ article 10 and 11 rights through arrest). The Supreme Court has, however, provided a helpful non-exhaustive list of relevant factors to be considered, including:

  • The extent to which the continuation of the protest would breach domestic law. Is there, for instance, any threat of violence from the protesters or a risk of clashes with counter-protesters?
  • The duration of the protest, which may include the full duration of the obstruction including the time taken to remove protesters from the highway following arrest.
  • The degree to which the protesters occupy the land
  • The extent of actual interference the protest causes to the rights of others
  • The nature of the place where the obstruction occurred (noting the difference between residential and commercial areas)
  • Whether the obstruction was properly targeted at the object of the protest
  • The importance of the precise location to the protesters and their right to choose a location
  • The right to choose the place, time and modalities of assembly
  • Prior notification to and co-operation with the police, especially if the protest was likely to be contentious or to provoke disorder

From a policing perspective, the decision to arrest is entirely fact sensitive and an arresting officer cannot be expected to undertake the kind of forensic assessment of all available facts that a charging officers would make. Section 24 PACE requires only that the officer hold a reasonable belief that the protest is or is likely to become an unreasonable obstruction of the highway without lawful excuse.

Any officer who believes they have reasonable grounds to arrest a person for highway obstruction has a straightforward ground for believing arrest is necessary, namely to prevent an obstruction of the highway: S.24(5)(c)(v). Where a protestor has previously been warned they will be arrested, and yet is still committing the offence, s.24(5)(c)(v) will be met almost by definition.

The Ziegler judgment is therefore unlikely to have a significant impact upon how protests are policed. Rather, the primary impact will be upon the approach to investigating s.137 offences, and how Evidential Review Officers (‘ERO’) make decisions on whether to charge a suspect with the offence or not. In particular, investigating officers will need to place greater emphasis on evidence of disruption to the lawful activities of the target of the protest or on members of the public generally. EROs will thereafter need to be satisfied that there is adequate evidence of such a disruption before authorising charge.