Tattle-tale dog

My husband has a dog that's a tattle-tale. I've known about his behavior for years, but it's only recently that it occured to me that he's a tattle tale. It probably comes from working so much with kids lately. Anyway, if another dog does something he's not supposed to do, Shadow will bark until we come investigate. It namely occurs with dogs that pee/poop where they're not supposed to. Especially in an area that Shadow wants to pass through/around. He won't do it until we clean it up (or make him). Instead he'll stand there and bark to point out that someone ELSE has done something.