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
“Okay, so what cool plot idea do we use to determine who might commit crimes?”
“IDK, just anyone maybe? People who use the internet?”
Same way I look for weed in illegal countries; find hippies and dreadlocks.