Why Do The Police Not Know The Law?

Or is it simply that they are too lazy to feel like enforcing it?

Debbie said she reported the incident to Northumbria Police, but was told that that there is "nothing they can do." Under current legislation, a dog on dog attack is not a legal offence.

And they are wrong: 

But according to the RSPCA, a court could prosecute if a person believes they would have been injured if they tried to stop a dog attacking their animal. Debbie continued: "They said they would only get involved if a dog attacked a person, unless it can be proved to be a dangerous dog.

"It clearly is dangerous, and I told them I hope it's not a child next time. I intend to get back in touch with them and push for more action."

Why should you have to?