Because in hardware IP travels with the machine. Opening one, potentially reverse-engineering it, or even just looking at it revealed quite a bit of information

Because in hardware IP travels with the machine. Opening one, potentially reverse-engineering it, or even just looking at it revealed quite a bit of information (for exemple the famous forward-facing camera, that we were waiting for on the 3GS last year), which were trade secrets of Apple until they were publicly revealed by Gizmodo. That's clearly against the law.