The legal issues arise from the owner of the greyhound - if it was agreed (usually in writing) that the animal will be euthanased and is not the owner can sue for <insert legal bit here>
The reason being
- the dog could be put back on the track and could turn into a winner
- the dog could breed and make mini winners
- if the dog was to get out and injure other animals the original owner and the institution is still responsible
The list goes on......