In which cases do you consider piracy legitimate?

[Veknoid_Outcast]

Ka-pi96 said:

When you already own it. Which is also the only time piracy is legal, so yay for that

Technically, the owner of a game can produce a digital back up to protect him or herself in the event that the physical copy is destroyed. But that digital copy must stay in the possession of the individual. It cannot be distributed across the internet.

So, even if you own game X it's still illegal to download a ROM of game X.

@OP: under no circumstances is it permissible, in my opinion.