It would ordinarily be unlawful to use section 58A to arrest people photographing police officers in the course of normal policing activities, including protests because there would not normally be grounds for suspecting that the photographs were being taken to provide assistance to a terrorist. An arrest would only be lawful if an arresting officer had a reasonable suspicion that the photographs were being taken in order to provide practical assistance to a person committing or preparing an act of terrorism.However, this entertaining short video suggests that these guidelines are not always being followed in practice:
There are a number of reasons for concern about this. First, is that camera phones are increasingly being used to provide evidence of police misconduct and hold the police to account for exceeding their powers. The police should not be capable of hiding behind legislation like this as a means of evading responsibility for their actions. The police are public officers acting in a public capacity and that means that they must visibly adhere to certain standards of conduct. And this is one way of ensuring that they do so.
Second, this seems like an extraordinarily poorly drafted section. Presumably (and I am guessing here) the aim of the section is to prevent the passing on or publishing of specific information (name, address etc) about identifiable members of the police or armed forces that might lead to them becoming the object of a terrorist attack. I have in mind something like publishing personal details about police officers engaged in specific counter-terrorism activities or something like that. If this is the case, there must surely be a way of drafting legislation in such a way as to make this clear - and to rule out the possibility of looser interpretations. If the police are to blame for interpreting the section more broadly than this, some responsibility must also lie with Parliament for making it so easy.