Does the dog's owner not also have affection for it?
Anyway, legislation for this kind of thing would be a nightmare. Any law that would award you another person's dog based on affection could award me anything I could ever want, based on my actual of falsified affection for it (assuming a pet is treated the same as any other property).
I would use that law to take people's computers. I obviously have more affection for them than the people who only use them to send annoying emails to all their relatives.
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"If knowledge can create problems, it is not through ignorance that we can solve them." - Isaac Asimov