Here are some regulations for hotspot implementations in Spain that you have to watch out for if you want to deploy a captive portal in Spain.
Need to notify Network Regulation Authority
Not a legal requirement, but recommended by authorities
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 internet browsing history
Not required. However to be reported if seen.
Logs available on government request
Yes, to be delivered on request in a secure way
Data to be encrypted and secured against unauthorized access.