In my experience as a library employee, there had to be a strong case that somebody was disrupting other patrons' abilities to use the library / creating a host

In my experience as a library employee, there had to be a strong case that somebody was disrupting other patrons' abilities to use the library / creating a hostile environment before they could get kicked out. Coming in falling-down-drunk, stealing stuff, or looking at porn on the internet stations was pretty clear cut, but sometimes the line was fuzzy.