Lawful means you follow a particular code or set of rules that define and guide your life. I don't see why that's so hard to grasp? The set of laws, whether bushido, chivalry or divine edict don't matter... only that you've chosen to follow them through your behavior.
And breathing requires you to open your mouth....of course we still need to specify that one needs oxygen to live.
So what we need to do is not add abstract alignment restrictions, but define WHICH set of laws we're following. Which again...is EXACTLY what I wrote up above....and is EXACTLY what I wrote in half a dozen posts in this thread.
Lets say we have a Paladin class that we want to
only be lawful good. Well, we don't know what defines lawful or good yet do we? So the Paladin must follow a code of conduct...so from whence does this code come from? The god or religion that they choose to follow.
So what we really need to do is say that the Paladin can only choose to follow a LG
deity. This deity defines exactly what it means to be "lawful good" for all of it's followers. Be that following only the deity's laws, be that following the laws or the land, or some other ruleset.
So in order to achieve the LG restricted paladin, all we have to do is say that a Paladin must follow a LG deity, who then specifies the specific code of ethics the paladin must follow. Theres no restriction on the
Paladin or the player to be LG, there's only a restriction that they must follow the rules as defined by their god. In the multi-deitstic world, the followers of two LG gods may be similar, but there are still going to be differences because of how that god/religion defines what it means to be "lawful good".