@JungleBoi I'm not sure where anyone brought data limits into the discussion in comments here regarding open WiFi. That's the least of one's worries when there are other risks that may involve police and courts.
Regardless of how much courts may separate one's public IP address from their personal identity, the value of that IP address as a lead in investigations will never be fully negated. If there is child porn being hosted from your public IP, or that IP is identified as the source of online terrorism or hacking activity, there is no way you will convince any reasonable court that police should not investigate what is happening on your network.
Charges may never be brought against you in court, but your network and computers are still valuable material evidence, and you a material witness, in any case involving the use of your network to conduct illegal activities. You and your equipment will, very rightfully, be detained and investigated to assess the degree to which you are or are not directly involved in those activities. Afterwards, you may indeed be free to go - even unscathed by any arrest record or actual prosecution. But, you will most likely spend several hours (if not days) talking to the police, and your equipment could be confiscated for much longer, before it all gets sorted out.
If laws were written to exempt open WiFi networks from such investigation, they would provide anyone who wishes to use the Internet as an avenue for crime an easy defense to avoid investigation even if the crime was traced to their own home's IP.