Off lead dogs should never go up to an onlead dog uninvited because you do not know why that dog is on a lead. If you can not stop your dog going up to on lead dogs, then that's your fault. However, I think that off lead dogs should be allowed to greet each other, unless either owner says that it is not ok. I think if an onlead dog is aggressive, it should be muzzled. It's not another dog's fault if it's owner hasn't taught it not to interact with onlead dogs. Aggressive dogs should not be off lead at all around other dogs, it's too risky.

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I OWN A CHOCOLATE ROAN COCKER SPANIEL
RIP David xx Run free at the bridge. Love you always xx 19th February 2011
RIP Jack and Mickey xx Run free at the bridge. Love you forever xx 20th June 2011