[Coda]

It's actually not illegal to POSSESS ROMs / ISOs. What's illegal is DISTRIBUTING them.

If you have a Blu-Ray drive, you can actually read PS3 discs as-is, legally. If you're using an official disc, the only thing about PS3 emulation that's iffy on the legality is the need for a BIOS image -- your right to play PS3 games without Sony hardware is actually a LEGALLY PROTECTED RIGHT, as long as you legally acquired the content.

The PS One, on the other hand, has a fully free reimplementation of the BIOS available in emulators now (that actually works better than Sony's official BIOS). If you have the PS One discs yourself, and you either put them in the drive or you rip them yourself, then there is NOTHING ILLEGAL AT ALL about emulating PS One games. (I think PS2 is in the same place in that regard but I've not done the research to be 100% certain.)