For the most part though, what protects journalists are the same laws that protect non-journalists. As journalists are involved in the judicial process, the finding of the courts are applied in a way that they would apply to anyone in that situation, not just journalists.
Another way to interpret this: the actions of a concerned citizen documenting people breaking the law. Example: If you saw a woman being chased by a man waving a knife in the air, and you started filming it, and they both ran into a building marked "PRIVATE - NO TRESPASSERS", should the person documenting this event simply wait outside? Or follow them in, at the very least to document what appears to be an attack, and potentially help? Would this person be charged with trespass? (IANAL, but you can see how regardless of a 'journalistic standard' these situations could become less than simple)
The protesters intent was to protest, and the reporters intent was to publish journalism on the protest, on a matter of significant public interest too.
Many people have no problem seeing the difference.
In my opinion, neither group should be charged in this case, but certainly not the journalist.
It's possible that his intent was to protest AND to publish journalism. What's the dividing line between protester and journalist?
For example, imagine an embedded journalist with a group of guerrillas that perform war crimes. At what point is the 'journalist' culpable for the crimes of the group? If the 'journalist's' intent is the making propaganda pieces for the group, is he still a journalist? If he takes up arms with the guerrillas, is he still a journalist?
I'm not saying this guy is a criminal, just stating that it may be a bit of a grey area depending on how much he is affiliated with the group.