Lots of confusion in this question. Where do I even start ...
First of all, what do you mean by "this"?
You mention Napster and Limewire. These are things. Things cannot be illegal. Actions can be illegal.
A certain action is illegal if there is a paragraph in the applicable jurisdiction that forbids it.
It might be illegal to manufacture, own, fake, destroy or distribute a thing. But a thing on its own cannot be illegal. What would that even mean.
So who did what, which jurisdiction is applicable and which paragraph forbids it?