London police say Thunberg was arrested for holding a placard in support of the banned organization Palestine Action, in violation of Britain's terrorism laws.
The demonstration was said to have taken place in support of members of Palestine Action who have been on hunger strike in detention for a number of weeks. According to Sky News, Thunberg could be seen holding a sign that read, "I support the prisoners from Palestine Action. I am against genocide."
Terrorist-labeled
Palestine Action is listed as a terrorist organization in the UK. The ban has been condemned by critics as an attack on freedom of expression.
Supporters of the organization have staged a series of protests across Britain since early July, when Parliament banned the group under terrorism laws. The decision came after activists broke into a British air force base and vandalized two tankers.
It is forbidden to participate in the group and to publicly express support for it. On October 5, almost 500 demonstrators were arrested during a protest in London in support of Palestine Action.
Can result in imprisonment
There are several ongoing legal proceedings against people who showed support for the organization by holding up a sign with the same message as the one Greta Thunberg held up - which could result in six months in prison, according to the BBC. But there are currently no indicative sentences.
Terrorism researcher Magnus Ranstorp says it is difficult to speculate on what legal penalties Greta Thunberg risks. But in general, the range of penalties can vary from fines to long prison sentences.
There could be serious consequences; the British are strict about these things. But it's hard to say exactly what it could result in without looking at similar cases.
