You have to be very careful with the word suspect here. No crime has been committed, not even alleged. The allegations are that the arrested may in the future cause disruptions - it’s currently even unclear whether these acts are crimes, misdemeanors or even public demonstrations and as such protected by law and the constitution. Legal opinions and court decisions are all over the place.

The jail time is even more problematic given that the acts that the imprisoned may commit in the future are not punishable by prison time in practically all cases.

(As a side note: I would also be extraordinarily careful citing an article in the Stern, which cites allegations that the Welt published, without having at least a second source that confirms it)