Allthough they are legal in this country they can only be used where there is a valid reason like protecting crops or livestock. By having one in a private garden may not be reason enough so they may be breaking the law. May be worth asking The Wildlife Crime Officer.
There is a website that is trying to ban them at:
http://www.againstcorvidtraps.co.uk/Caution there are some sickening scenes against the birds in one of the video clips
A Brief Outline of Larsen Trap Legislation
The General licence is issued by authorities in England, Scotland, Wales and Northern Ireland to allow the larsen trap to be used for the control of: Crows, Magpies, Rooks, Jackdaws and Jays. Wood pigeons and Sparrows were removed from the legal decoy list. All Larsen trapping operations carried out under the general license must have a reasonable purpose. Simply hating Crows or magpies is not a valid reason. Protecting livestock or protecting crops is a valid reason.
The General Licence states that welfare requirements of the decoy must be taken into account. Decoy birds must be provided with food, water, shelter and a perch. As with all traps the Larsen must be checked at least once a day. The best times to check are one hour before sunrise and one hour after sunset. Be aware that some traps can be filled with trapped birds many times a day, so keep checking during the day.
The Larsen trap is governed by a general licence under the Wildlife and Countryside Act 1981.
Captured birds provided they fall within the legal quarry list may be dispatched by an approved method. Any non target species must be released immediately!!
There is no set size to decoy cages.
When not in use Larsen traps MUST be rendered incapable of catching, i.e. no bird can push the trap door open and become caught as a result. Top opening traps can be turned upside down or have the door springs unhooked. Best practice is to store your traps when you have finished your trapping season.
General Licences:
General licences are issued by government agencies to provide a legal basis for people to carry out a range of activities relating to wildlife. By definition you do not need to apply for general licences but you are required by law to abide by their terms and conditions.
General licences are renewed annually in England, Scotland, Wales and Northern Ireland. These general licences are made available on the websites of the relevant government agencies and include those general licences relevant to the all year round control of ‘pest birds’ such as magpie and woodpigeon. Control methods allowed under general licence include the use of larsen traps and multi-catch traps.