HA!

They are border collies, very smart dogs. They know they could if they wanted to, but that they shouldn't, so they don't.

I used to have 2 Norwegian elkhounds at our other house. I don't think it was invisible fence, but some other brand. The smarter of the 2 would go to the fence where it would make the noise, and lie there till the noise drained the battery. When it would stop, he would cross the line.