what is “broadcasting” where WiFi is concerned?

So, not to belabor a point, but the final post in this “man gets hassled by cops for using WiFi outside of a closed library” is up. In a weird turn, the Atheneum has now posted a policy saying, in essence, their WiFi hotspot isn’t supposed to be used when the library is closed. Am I missing something here? Isn’t it easy enough to just shut it down if you don’t want it to be used? Or password protect it after hours? Are the police going to enforce this policy? Is there any legal precedent for that? What’s going to happen when the whole island becomes a hotspot? Or is this enforcement of free WiFi supposed to drive people towards the pay services? I’d be really interested to hear from librarians who offer WiFi: What is your policy for patrons using WiFi 1) outside the library, and additionally 2) when the library isn’t open? Thanks.