Mixed up thinking
It seems to me that there are two very different things being dealt with here. One is about whether it is legal for a WiFi operator to offer free access to a service via their contracted ISP whilst the other is about how you know you are
On the first point :-
"Mac Síthigh argued in his paper that such legal uncertainty threatens not just the ability of commercial organisations to use free Wi-Fi to attract customers, but local authorities' ability to offer access to people who otherwise might not have it."
This would appear to be firmly in the area of civil law and would appear to be governed by the terms and conditions of the contract that the WiFi operator has entered into with their ISP. I would have thought that any local authority or business would have considered this. It's certainly true that there will be grey areas for small business - for instance, can a B&B, cafe or Guesthouse use a normal domestic account for offering what amounts to a business service. But that will be primarily a civil law matter and not one of criminal law unless there is some conspiracy to defraud the ISP. I suspect similar issues arise with a householder sharing their ISP connection with their neightbours - that may fall foul of ISP T&Cs, but it is a civil matter.
The second point is different again - just how do you know that there is implicit approval by the WiFi operator for free access to a publicly available network. In some cases it will be obvious - like notices to that effect. However, in other cases it will not be so. Clearly if a WiFi connection's security is hacked, then that is clearly not an authorised access - but what about those WiFi connections which are left open by accident? How do you tell whether that is deliberate or not? Maybe some explicit system (like network naming) should be used.
Of much more legal concern in a criminal sense over making a WiFi access point publicly available is surely the issue of when it is used for criminal activity. I doubt that this is a problem for truly public services, but a householder who allowed their WiFi service to be available for others who then used it for illegal activities could find themselves involved in unpleasant investigations (at the least). Given that thse sort of investigations are heavily reliant on ISP records and logs, the first point of call is very likely to be the person contracting the service. For this reason, then I think householders would be wise to be very careful over the informal sharing of WiFi connections with others than those who can be trusted. It should be added that this attention could also include those seeking civil remedies for such thing as breach of copyright. It may not be an area of strict liability in law, but dealing with the consequences could still be very unpleasant and costly.


