Here are some regulations for hotspot implementations in Belgium that you have to watch out for if you want to deploy a captive portal in Belgium.

Country
Belgium

Need to notify Network Regulation Authority
Yes, need to fill out the online notification of services. 

Authentication required
Recommended logs should include identification information

Logs policy (duration, location & how)
Duration: 12 months, then delete or anonymize
Location: in European Union
How: Identification of user (Any user ID, name, or phone number), type of communication (internet usage), connection time and duration, IP address and port number allocated to the user or device connected to the Internet, location of the hotspot, amount of data (can be over a session, or over a period of time).
Do not keep the user's internet browsing history

Copyright infringement
Not required. However to be reported if seen.

Logs available on government request
Yes, to be delivered on request in a secure way

Privacy
Data is to be encrypted and secured against unauthorized access.