I assume the question relates to the British Isles so Screwjacks statement of the position in Miami FLA (from profile) may mislead. Even there I believe the FCC take a dim view of intercepting celphones and disable scanners for the US market accordingly.
The Isle of Man is a separate legal jurisdiction to the rest of the UK, so the position may be different again. In the UK it is illegal to listen to anything except licensed broadcast stations, amateurs and certain weather x/missions (not sure if this includes Volmet etc). The relevant legislation is the Wireless Telgraphy Act and the Interception of communications Act. See the Radio Communications Agency's leaflet RA169 on receive only scanners available on their website
http://www.radio.gov.uk/. I think there is also something specific to aviation but I can't find the reference.
In practice enforcement depends on what you listen too. Eavesdropping on ATC is generally ignored as harmless, the number of scanners in open use in spectators areas and at airshows is testimony to this. Indeed the CAA are thouht to recognise the value of this as a trainig aid for wanabee pilots and are reluctant to back prosecutions. Get caught with Police FRX in your scanners memory and you are facing confiscation and an criminal record.
Aside from morality there are separate offences for passing information on to others. Respectable scanner hobbyists are scrupulous about that particularly if tabloid publication is possible. Unfortunately there are always the less fastidious particularly if money is involved as well as the young and stupid. Some will I am sure recall the tragic accident to a Bandeirante out of Leeds in 1995, where a teenager in Kendal claimed to have heard distress calls on a scanner given to him for Christmas.
[This message has been edited by Airbanda (edited 07 June 2001).]
[This message has been edited by Airbanda (edited 07 June 2001).]