Abusive library patrons mixing books, booze and brawling are partly to blame for more than 200 trespass notices issued in Dunedin since 2011.
The city council has issued 232 two-year trespass notices, including 206 at the central city library, of which 70 remained in force, statistics released to the Otago Daily Times showed.
Council libraries customer experience manager Mike Collett said most of those trespassed were involved in incidents of abusive behaviour, aimed at other customers or staff, as well as petty theft, vandalism or other "mindless" behaviour.
Some had brought alcohol or drugs into the library, and court action had followed in some cases, particularly when theft was involved, he said.
"It's generally petty and just mindless behaviour."
The number of notices issued each year was not "out of line" with libraries in other centres, but could be explained in part by libraries' changing patterns of use, Mr Collett believed.
Free internet, in particular, attracted more people who were "not traditional library users", he said. "Then there's potential for behavioural problems and friction between individuals or between them and library staff."
Staff usually issued warnings first, or asked offenders to leave for the day, but recidivists were trespassed as a last resort, he said.