If the description that is given was accurate, he made two of the basic errors in interpretation - conflating 'lawful' with "obeys the local laws", and enforcing an alignment shift for a single minor transgression. So, yeah, in my opinion he didn't appear to understand alignment.
And yet, the guidelines in the book do emphasize that obeying laws is a lawful act. How much guidance does it give on what point merits an alignment shift?
Look, to give an example I have my own experience with - I played Living Greyhawk. In the game, you could not play an evil character. However, non-evil characters potentially had access to spells with the 'evil' descriptor. Such as Deathwatch, an otherwise relatively harmless spell which simply reveals whether creatures are alive, dead, dying, undead, or other (such as constructs).
And yet, it had the evil descriptor. And so some folks argued that casting it was an evil act, and some DMs wouldn't allow it since doing so would make the character evil and thus they would need to be confiscated, etc. Others felt that using it was relatively harmless, and that even if it was an evil act, hardly merited an alignment change. But what if you used it a lot? What if you used it often, but used it to fight evil enemies and accomplish good deeds?
We've got a similar thing here. If a DM believes "obeying the law is acting lawful" and "doing so over and over and over again will eventually turn your lawful"... they don't match your interpretation of alignment. But the rules seem to allow for that interpretation. And the rules are what encourage the DM, in the first place, to be even making that decision. And that is where the system is at fault, in the end.
Then your DM is wrong. Such a character would be of a Neutral alignment, neither Lawful nor Chaotic. And Neutral is a perfectly valid alignment for a 3e barbarian.
But then we get into the tricky element of lawful and chaotic activities balancing each other out. 90% of the time, he acts lawful. Occasionally, he is a frenzied berserker and flips out. Do those balance down to Neutral? Or should he be Lawful most of the time and occasionally flip to Chaotic?
Or what about if we flip to the other axis. 90% of the time I go around helping people. 10% of the time I go around poisoning urchins. Does that balance out to Neutral? Does the evil act override all the good and kick someone to evil
I can totally understand someone liking the concept of alignment, and feeling their group has a sound enough agreement on the matter to never cause a problem. But I don't think you can simply dismiss the fact that many, many different arguments over the subject have come up over the years, and even the strictest reading can allow for multiple, contradictory, interpretations.
There is no system that doesn't allow a DM to make bad calls. There can be no such system.
Sure, but the system certainly influences what calls a DM will make. Telling the DM that they, rather than the player, get the final judgement on how a character should act - I'm saying that is planting the seeds of trouble.
If the rules said, "Here are some alignments that players can use to guide their characters" rather than "Here are some alignments that players must adhere to, since there are specific mechanical effects that affect them"... you wouldn't end up with DMs getting into arguments with players over alignment, or making 'bad calls' about it.
They might make bad calls in other areas of the rules. Or they might not - again, half the problem is that alignment is an intentionally nebulous area with room for many interpretations. DMs who smoothly run AoOs and Grappling might find themselves stumbling when dealing with alignment, which doesn't give them any ultimately codified answers to rely upon.
Even if you maintain that some of the examples seem in this thread are, in your opinion, just bad calls by the DM - I think there are many, many other examples out there where it truly does come down to two potentially valid interpretations. Are certain monsters natively evil? Is it ok to kill someone who 'detects as evil' on that basis alone? Is a rebel attempting to overthrow the government, yet who has their own complex code of honor, a lawful character? Is it really neutral to murder someone one day, and donate to the poor the next?
There is a reason alignment is known to be one of the most argued over elements of the game. And I think a lot of that comes down to
encouraging the DM to be making these calls.
So, yes, the system can't ensure that everything will be perfect all the time. But introducing something fundamental to a character's identity, providing poor or even contradictory interpretations of it within the rules, and then tying it to mechanics such that the DM is encouraged to 'keep watch' and make sure a player follows their alignment in a way that matches his interpretations... yeah, I think that is setting things up for trouble.
And while a system can't be perfect, I would certainly prefer one that does better than that.