The police are constantly collecting the personal data of demonstrators, like their addresses, citizen’s service numbers, and date of birth, even if they’ve never been arrested. The police also collect data on some demonstrators' family members, like parents or children.

The police get the data from the Personal Records Database (BRP), a database containing information on every resident of the Netherlands. According to the police, accessing this database is necessary for the performance of its duty.

Before the people became active in protests, the police only requested their data for things like bicycle fines. After they participated in demonstrations, the requests for their data skyrocketed. For example, the police requested personal data on coronavirus protester Michel Reijinga over 1,400 times in two years.

Data of demonstrators’ families are also requested. A police spokesperson could not explain why.

The involved demonstrators are shocked.

In response, the police told the journalists that the purpose of the data processing is recorded “very generally,” for example, “to maintain legal order.”

https://nltimes.nl/2023/03/10/police-collecting-demonstrators-personal-data-large-scale