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/letz...
Additional Context: The state government of Bavaria (and several others around that same period, with similar ideas) passed a controversial reform of police laws in 2017-2018 (It was polemically called "The strictest police law since 1945").
It included changes such as:
increased allowance of use of personal data by the police forces.
allowing the police to openly film and photograph people participating in public gatherings.
allowing the police to infringe on postal secrecy and to confiscate mail without a person's knowledge. (if given permission by the courts)
allowing the use of police spies. Including even entering people's homes if given permission.
As well as making previous restrictions such as on "probable danger" way more lax.