I had to take this weird law class in college, and anyway one of the assignments had been to find weird laws, find out what they really meant and then write a paper on them.
Sorry - but I'm not a cat fan so hope this doesn't offend any cat lovers.
There is a law that exists that says if a police officer see a cat it is his duty to kill such a cat.
The reason for this law, it had been made during some major plague breakout and it was blaimed on cats, there had been a huge population jump in cats about the same time as the outbreak.