I think the Paladin Code IS a set of hard-and-fast rule. But the wording within it is often vague and explicitly allows for intrepretation. Some examples:

How do you show respect? (rule 9) I think it's easy to intrepret that meaning you can still disagree with their laws while being respectful. There just needs to be something to show that you are being respectful. Going on a bloody crusade and slaughtering every Tribunal you come across, wherever they are at and whatever the situation, would probably get a paladin in trouble. A paladin in Outlander wouldn't work, because Outlander requires that you disrespect the laws. But you can certainly get away with breaking the Tribunal laws, depending on how your character intreprets "the law."

What is a worthy cause? (rule 5) Obviously another rule that is open to broad intrepretation. What makes for a worthy cause? You can intrepret what constitutes worthy causes for your paladin, but then you have to fight for them.

What is a basic necessity? (rule 2) For some paladins a basic necessity might include four weapons to cover different vulns and resistences. For another it might mean he only carries a stick.

Number 8, however, is pretty clear. Don't lie.

As far as number 11 goes, I personally don't think a paladin can justify being empowered by an evil god. Gods have to roleplay too, and we have our own IC things going on that surface eventually (often in the form of gechos and/or quests). To get empowered by Eshval, you have to walk by the disembowled guy making his guts into balloon animals. Come on now.

Now however, I do think many evil gods can justify doing it, because to them you're just something they can manipulate in the long run. If you are a paladin empowered by an evil god, I think you (as a player) should expect to have to make a decision between your god and the light eventually. But when I'm personally roleplaying, any goodie following an evil god is immediately and permanantly suspect in my book. If you're a Grurk-following paladin in the Fort, and Grurk comes and attacks Aarn and tries to lay waste to the Fort, what are you going to do? Rule one says you have to be loyal to your god and your beliefs. It doesn't say "your religion and your beliefs." It specifically says "your god". If you believe in the goodie dogma while following an evil god, don't those conflict?

But then again I'm not an evil god, and that's just my opinion as an individual.

Anyhow, my point was that while the Paladin Code is NOT a bunch of "suggestions" that you can follow if you want to - or not if you don't - it is broadly worded and open to a lot of intrepretations, ideas, and roleplayed justifications. But you still have to follow it 100%, in your own way.