Wow.
I just post that and two people immediately come here to tell me that if my Paladin did that I would "not be playing the magical wizard make-believe pretend" the right way.
Way to totally miss the point guys. The point is that if a player wants to make a Paladin who does that, then who are you to say that they are playing pretend wrong?
Here is a fact: it's a game. If you don't think the paladin class adequately represents the vision of a dead guy whose paladins probably didn't live up to their own code, well... Good for you.
If someone has an interesting, fun, and engaging idea for a character... Well, no. You're exactly the sort of people who would take a fun, well built character with well written backstory that is well roleplayed and focus on nothing but the fact that the Paladin being played was just plain good and wasn't lawful at all.
This is a fantasy roleplaying game. And it should be open to the widest range of possible choices. If you want to declare that in your world all Paladins are lawful good, go for it. Please dont try and get every single person who plays D&D on this entire planet, in every country and culture, to adopt the restrictions of your setting.