It was always my assumption that the CG ones were from a different planar pact than the Devil-themed ones. I could see a Fae powered warlock being a very chaotic good type.
To that end, I do agree that there are likely in any campaign world Lawful powers that would make a deal and make some Lawful Warlocks. I always thought it would be better set like Clerics where you needed to be within one step of your pact source.