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?
Edit: You have since edited your comment but let’s still start there.
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?