/me does that unusual thing of actually reading the article … ah, here we go “Protestors physically blocked oil tankers in the harbour… When the protestors were ordered to move to allow vehicles to pass, Greta was among those who refused. She was then dragged away by police.”
So she wasn’t peacefully protesting, which by the way IS legal in most places; she was being obstructive, somewhat like those Just Stop Oil muppets who glue themselves to roads. It’s fine to protest. It’s not fine to prevent others from living their lives, and that’s why she was prosecuted.