ok, OP here with the law
Quoting for England, although similar rules apply for wales, Scotland and NI.
This is to implement EU regs, although Eire still allows kitchen waste- one EU rule, loads of different implementations !
Feeding catering waste comes under the Animal by-products regulations 2005, Part 3 deals with catering waste
11.5
It is an offence for any person to allow livestock to have access to any catering waste or other animal by-product except—
(a)manure;
(b)milk or colostrum;
(c)digestive tract content that has been applied to land provided that livestock are not allowed on to the land for at least three weeks after application; or
(d)compost produced and applied to land in accordance with regulation 16 provided the conditions of that regulation are complied with.
(6) It is an offence for any person to allow any animal to have access to material derived from catering waste or other animal by-product in a biogas or composting plant, except that it is not an offence for wild birds to have access to the material during the secondary or subsequent phase of composting.
(7) In this regulation “livestock” means all farmed animals, and any other ruminant animals, pigs and birds (other than wild birds).
Defra's strong interpretation is that "catering" includes domestic premises, Eire takes the view that "catering" means commercial premises.