The 1996 Regulation can be found at
http://www.opsi.gov.uk/si/si1996/Uksi_19961104_en_1.htm
"Citation, commencement, extent and interpretation 1.?(1) This Order may be cited as the Prohibition of Keeping of Live Fish (Crayfish) Order 1996, shall come into force on 29 May 1996 and shall extend to England and Wales.
(2) In this Order "crayfish" means a freshwater decapod crustacean of the Families Astacidae, Cambaridae or Parastacidae, other than the species Austropotamobius pallipes (commonly known as the Atlantic stream, or white clawed, crayfish).
(ie. our endangered native crayfish is excluded from these regs - just don't go near them, an entirely justified world of pain and fines awaits those who do)
Prohibition of keeping of crayfish
2.?(1) Subject to paragraph (2) below, no person shall keep any
live rayfish, except under the authority of a licence granted by the Minister.
(2) The prohibition specified in paragraph (1) above shall not apply to crayfish of the species Pacifastacus leniusculus (commonly known as the signal crayfish) kept within those parts of England and Wales which are within the postcode areas set out in column 1 (and described in column 2), as read with column 3, of the Schedule to this Order.
The schedule referred to being found at:
http://www.opsi.gov.uk/si/si1996/Uksi_19961104_en_2.htm
Which I think (though I have hardly sat down and checked it !) corresponds to the green areas of the map shown on the other page mentioned above.
So the upshot is that if you are in any of the postcode areas set out in the Schedule to the Regs / the green areas on the map you can harvest Signal crayfish for the pot quite cheerfully and without needing licences etc.
If outside these postcode areas you have to ask the EA for a licence before doing so.
The licence, if granted, is free
- how often does that happen with government ? ? ? shows how much the EA don't like Signals....
But may not be granted if there are reasons not to, eg. risk of disturbance of the native white clawed crayfish in the same water etc.
That said note that the prohibition, even if outside the permitted postcode areas, only applies to the "keeping" of "live" crays. So there would appear to be a loophole. If you trap and kill Signals forthwith on the bank you seem to be OK as the regs do not apply to dead Signals.
One little wrinkle that amuses is that it logically follows from the original act and the regs is that it is unlawful to put a signal crayfish back in the water once you have caught it or to release it on the bank, as in doing so it is plain that you know it will inevitably return to the water, albeit under its own steam.
It is also unlawful (outside the permitted postcode areas) to keep it live....
Good old Catch 22
So if you want to avoid committing an offence either way it seems that you have no alternative but to kill the damned things if you do catch them !