Paladin and rogue in the same group - what's allowed and what's not?

[hamishspence]

No, it doesn't. Killing an [EVIL] outsider is a non-evil act. All the time. Every time.

Except when it would qualify as Murder.

"Murder is an Evil act" may override "Kiiling a fiend is always a Good act" from BoVD.

Nonevil fiends certainly exist- in fact, WoTC statted out a fiend paladin, no less.

If you walked into A'kin the Arcanaloth's shop and murdered him as a paladin, you could try to use that argument. But in any game I run, you'd be making that argument as a fighter without bonus feats, not as a paladin, because you would have fallen for murdering someone who has not demonstrably harmed anyone. The same applies to killing a random succubus just because you happened to see what she is.

This would work quite well in a Sigil-centric campaign- where fiends and celestials interact relatively peacefully in the city. There, you might find them arguing, but generally you won't find them fighting each other.

Some fiends are more loose in their alignment than others- Cambion Demons, who are less human than half-fiends, but still have some human blood, have as much as 10% of their population be nonevil, according to Expedition to the Demonweb Pits.