Believe it or not, that's actually legally very difficult to prosecute. NSP and XCI files are unusable without a signing key that attests the owner has purchased the game, which makes them a perfect candidate for the "backups and archives" clause of the DMCA act.
On the other hand, what Bowser did was pretty much indefensibly a crime. He distributed Nintendo's private signing keys to customers for a profit, something he knew was privileged IP, but he continued to sell them anyways.
> NSP and XCI files are unusable without a signing key that attests the owner has purchased the game, which makes them a perfect candidate for the "backups and archives" clause of the DMCA act.
This is false. NSPs distributed by pirates contain the decryption ("title") key (there is no signing key that asserts ownership, only integrity/validity), and XCIs are not encrypted by a title key at all.
You never know, Sony's private keys were found because they failed to implement ElGamal correctly (reused the nonce, making it possible for the signing key to be determined from two official signatures). I doubt you'll find any of their secrets encoded directly in the binaries they ship, but a company as old-fashioned as Nintendo will probably run into crypto trouble at some point.
I think Nintendo would have a hard time pressing charges. As long as you haven't tampered with the DRM mechanism, there should be no problem with copying and even (in a limited capacity) distributing it.
On the other hand, what Bowser did was pretty much indefensibly a crime. He distributed Nintendo's private signing keys to customers for a profit, something he knew was privileged IP, but he continued to sell them anyways.