In the German state of Bavaria, dozens of people are in 'preventive detention' because they might otherwise engage in climate protests, specifically around the car industry exposition IAA in Munich.
Apparently possible for a month there...
https://www.zeit.de/gesellschaft/zeitgeschehen/2023-09/letzte-generation-bayern-praeventivhaft-gewahrsam
They should put some kind of mark on all those suspicious people and their house, to also let other people know who lives among them.