They are not, and I speak from being attacked in my own yard by one who tried to come over my fence at me.
He didn't make it but his head was over and I almost lost three fingers. I realized the only way to save them was to rip them out of his mouth. While I went to the ER, animal control took him away for ten days but brought him back because the landlady, who was also attacked earlier, didn't report it.
The pit bull is still there and angry as ever when I get close to the fence. He and his female mate got into it a couple of weeks ago and fought for twenty minutes trying to kill each other. The neighbors, who weren't home at the time, have two little boys who are about the age to get out of the house when Mom isn't looking to go pet the dogs. I shudder to think what will happen if one playfully pulls the dogs ears.
Certain substances placed in a meatball will solve the problem.