Pavane mentioned:

there are many tales of council staff posing as 'visitors' and prosecuting the club because they were allowed in. (Was this Entrapment?)

In a sense, maybe, but for legal purposes (at least in the US), it means that the investigator has induced a person to commit a crime who otherwise would not have engaged in the prohibited act. This is an oversimplification, of course, but that's essentially it.

Dave Oesterreich