Imagine and Hp laptop, or a Mac. Would it be legal to modify the case of the laptop, for example change the color, shape and the materials and resell it as "modified by blah blah", or "designed by blaha" or "Hp laptop by blah blah".
It will be written that it is an Hp laptop or a Mac, but in the case by "blah blah".
No software or hardware will be modified, only the appearance. Some buttons or LED's may be dysfunctional after appearance mod, but are merely covered by the case and are not removed from the motherboard.
Is it legal? The idea has nothing to do with laptops, it was just used as an example.