Slaughtering for food is not crime as per the law. But cruel treatment of living animals is crime.
https://www.facebook.com/lovencareanimals/videos/1296469477039428/
Unless customers object and move away from such shops whom you see receiving chicken from such suppliers, this evil will continue.
If you take such a supplier to the police, other traders will gang up against you. None can stop you for saying NO and going to another shop. Your NO will spread in time.