But what many people don't know is that private non-governmental agencies are not bound by these rules
Also known as the Batman exception.
I don't think Teler would have protested his competitor adopting the trick itself (magician interacts with shadow on screen but affecting the physical object casintg the shadow) -- he'd have expected credit ("This trick was invented by Teller") but wouldn't have claimed legal ownership. But Teller should be able own the theatre he creates.
The process would have been, the guy asks for Teller's permission. Maybe Teller grants it, maybe he doesn't. Maybe he sells a license to the guy. Same as with any other theatrical performance. But selling the trick to other people is akin to putting your name on the script to a recent play, running off copies and it and selling them.
Going after the guy for copyright infringement is icing on the cake. And that depends on whether Teller published it with a copyright symbol on it, or registered it with the copyright office, way back when. (Since 1989 registration hasn't been necessary.) It's possible a situation exists where the routine is in the public domain, but the method of achieving the illusion is patent protected. All Dogge needed to do in that case was figure out a *different* way of doing the trick... which is, ironically, most of Penn & Teller's act.
IMO he'd have a better case if he'd patented the trick; then he'd be an automatic winner if Dogge's version uses the same method. I think. On the other hand, there's a (probably weak) case to be made that Teller's copyright covers all methods of creating that same illusion.