"You wear your honor like a suit of armor, Stark. You think it keeps you safe, but all it does is weigh you down and make it hard for you to move."
Lawful Stupid is gamer slang (derived from the Dungeons & Dragons alignment system, but can easily be applied to characters in any role-playing game as well as fiction in general) for a specific way of playing a Lawful Good or, especially, a Lawful Neutral character, most infamously a Paladin. It is characterized by lack of common sense, following the rules arbitrarily without actually understanding them and just generally being an annoying prick. He's that guy who will stop a chase scene because he has to chastise someone that was jaywalking. Lawful Stupid players are one of the main reasons (along with asshole DMs) why people dislike the Paladin class. It can also be a jab at the fact that Intelligence is a common dump stat for Paladins in 3.5, since their MAD mandates high Charisma and Wisdom, the traditional dump stats of combat classes.
Although the iconic Lawful Stupid character is a poorly-played Paladin (Alignment requirement: Lawful Good), non-Paladin depictions are almost invariably Lawful Neutral, since this kind of characterization is a disappointingly logical extrapolation from a character alignment that can be summed up as "the Law is the Law and all that matters is that it is the law; whether or not it helps or hurts people is irrelevant, the LAW must be upheld!"
A lot of this really stems from a surface understanding of the Lawful alignment. While following the law is a lawful act, following the rules is not the end-all definition of the Lawful alignment. Lawful means orderly. So the type of person who religiously organizes their sock drawer would be considered Lawful. A Lawful person can disagree with the laws of the land, wanting to replace them with new laws. It's the desire for order and logic that matters. Of course these would be sensible Lawful people, and therefor not "Lawful Stupid".
How to avoid it while playing Lawful Good
Required Reading: The Discworld series by Terry Pratchett, in particular anything having to do with the Witches of Lancre or the Ankh Morpork City Watch. Granny Weatherwax, Sam Vimes, and Carrot Ironfoundersson are all (probably) Lawful Good, but all add their own twists on the formula. Carrot possesses such a high Charisma score that he can literally charm people into doing what he wants, but when that fails he tricks people into doing what he wants, avoiding a non-Lawful alignment by twisting the law into a pretzel when he can. Vimes follows both the letter and the spirit of the Law whenever he can stretch it, but isn't above committing illegal acts to uphold Lawful purposes. Granny is Evil by nature and Good by choice, and hates it. To combat this, she continually takes out her frustration on other people by acting like the entitled octogenarian that she technically is, avoiding a fall into True Neutral or Neutral Evil because witches are supposed to act a bit nutty, even the Lawful ones, and none of it matters as long as she does what's capital-r Right.
The AD&D book "The Complete Paladin's Handbook" has a section("Virtues", page 33) on the behavior and code of conduct a Paladin normally upholds; that of a gracious and well-mannered individual who respects good and the law, but is not on an endless crusade to uphold it. They would not upset a tavern just because they detected an evil presence within and risk causing chaos, for example.
Another way to play lawful good is to play your paladin like a modern soldier: able and willing to do anything needed to win, except as decreed by certain laws and customs of war (for example, the Geneva and Hague Conventions). Those laws still restrict the actions of a soldier but he is still expected to act with common sense in order to achieve victory and not follow orders that violate those laws.
How to avoid it while playing lawful neutral
This is arguably even harder than avoiding it whilst playing Lawful Good; at least Lawful Good types are supposed to balance their calling to law & order vs. their calling to good. Lawful Neutral types are categorized by their firm belief that law and order are the only things of importance, with morality being dismissed as insignificant next to maintaining of order. The primary key to doing so is to keep a proper perspective; traffic laws, for example, have their place in the scheme of things. When you are racing to prevent the nuclear annihilation of a city is not that place. Don't get so bogged down with legal minutia that you allow far greater acts of destruction and anarchy to occur in whilst you attend to the little things.
Judge Dredd can be a good example of this. For example, in the opening sequence of the 2012 Dredd movie, he pursues a car full of criminals but does not shoot at them until they collide with and kill a pedestrian, and even then only shoots to disable the van's tires. He doesn't shoot to kill until one of them threatens to kill a hostage and refuses to accept an offer to surrender. Also, when he sees a vagrant sitting outside the crime scene Dredd tells him not to be there when he gets back instead of arresting him because he has better things to do at the moment. Of course, when he's just doing the rounds on his birthday, he'll issue noise citations to children who sing to him because he is The Law (and then donate the presents he receives to an orphanage because he's not That Guy).
This is not to say that a Lawful Neutral character doesn't recognize when they break the law or go against the general sense of law (Law) when called to; they do, and they're likely to be annoyed by it.
Examples of Lawful Stupid
- The Inevitables, divine golem-like beings with the duty to enact laws and enforce contracts. There's a story of one named "Obligatum VII" (the seventh in its line because six times prior people had the common sense to stop him) who trying to free the BBEG in a campaign from the book Elder Evils. The story goes that some mages summoned an eldritch abomination named Pandorym to blackmail the gods, making a contract with it to destroy the universe when it was summoned. The wizards imprisoned Pandorym instead of finishing the ritual to let it loose so that it wouldn't destroy the universe before they were ready, but the gods just smote the stupid wizards the instant they were done imprisoning Pandorym so he's stuck. Well, Obligatum is here to set things right, and make sure that poor, imprisoned death machine gets the freedom it was promised to carry out its goal, which through some warped sense of honor it is willing to do. How exactly this does not bring him into conflict with another type of Inevitable, the Varakhut, whose job it is to prevent deicide is a whole other box of worms.
- The Harmonium from Planescape. "The Harmonium believes that peace is a better end than war. [...] If it takes thumping heads to spread the truth, well, the Harmonium's ready to thump heads. Sure, there may not be peace right away, but every time the Harmonium gets rid of an enemy, the multiverse is that much closer to the universal harmony it was meant to have." This attitude is how the third layer of Arcadia shifted into Mechanus, and the gods of Arcadia had to start over. Whoops. What's more, don't forget that they exterminated all non-lawful good and neutral species in the world where their faction originated. Some good.
- The Modron race, similarly to the Inevitables above, due to being extraplanar mechanical lifeforms who embody Lawful Neutral. Except they somehow have even less personality. Imagine a poorly-written chatbot with arms, legs and the ability to beat you over the head; that's basically a Modron. They can't even understand the idea that their assumptions may be incorrect.
- Helm, the Lawful Neutral God of Guardians and Watchmen from the Forgotten Realms has earned this kind of reputation in-universe. Nobody will ever let him live it down that, during the Time of Troubles, he killed Mystara, the Goddess of Magic, for trying to get back into the upper planes after Ao kicked them all out, despite the fact he knew that this would severely damage the fabric of reality in the process. As a result, wild magic zones and dead magic zones are commonly called "Helmlands". He also catches a lot of flak for the role his worshippers played in the massacres in Maztica, but that's not so much Lawful Stupid as religious bigotry and the priest's only daughter being sacrificed by one of the natives.
- The stereotypical Space Marine. Stealth is cowardice, frontal assaults are the only way to go. On the occasion they do utilize tactics like stealth, feints, and flanking, it's all to help the frontal assault succeed rather than the other way around. Retreating is never an option, even if it's to gain more cover. Some will never field psykers, ignore xenos, and some won't even cooperate with other Space Marine Chapters. A special case being Leandros.
- The Starks from Game of Thrones. When Ned Stark finds out that Joffrey and his siblings are incest born bastards, he does the most asinine thing possible and tells Cersei, instead of going to Robert directly. He also tells his daughters of his plan, which causes Sansa to blab to everybody. His son Robb Stark has even more fuck ups, namely executing one of his top generals when he should have kept him around (though said Karstark general undeniably disrespected his authority), failing to communicate with Edmure (though Edmure is incompetent), and blatantly breaking his promise to Walder Frey because he felt bad he screwed some other chick and decided to marry her in order to keep their honor intact (though Walker Frey is admittedly a backstabbing opportunist who might have betrayed him anyway as Robb was undoubtedly losing the war. Also, Walder’s choice to violate one of the most valued rules of honor that even pirates, thieves and murderers keep, simultaneously fucked over his own side by becoming the group absolutely nobody on any side wants to be associated with. Not even the people he betrays Robb in favor of). This kind of shit ends up with the Starks practically destroyed.
- An important qualifier is that these decisions aren't entirely motivated by stupid adherence to honour, with personal history heavily motivating the decisions or with the full consequences of the actions not being immediately obvious.
- The Jedi from the Star Wars Prequels are this, as they followed the Jedi Code - which was meant as a mere guideline - as a set of unbreakable rules and set out to completely repress all emotion in somewhat unfounded fear of those emotions leading to the dark side, when they should have acknowledged that which makes us human and simply taught how to use them positively. Such arbitrarily following of the code leads the Council to turn a blind eye to the various problems Anakin Skywalker was having, thereby unintentionally sealing their own downfall.
- Works set before the Prequels shows that this is hardly a new problem for the Jedi Order. Knights Of The Old Republic features a Jedi named Atris who's incredibly obsessed with following the code to the letter and wiping out the Sith. This leads to her being filled with bitterness and remorse after her best friend the Exile is kicked out of the Order, but also leaves her too arrogant to talk to anyone about it. Instead she starts to hide herself away in a temple filled with Sith holocrons to be alone and meditate, and since Sith holocrons literally exude Dark Side-tainted Force energy, she gets unknowingly corrupted into a Sith. Yes, she was so Lawful Stupid that it turned her evil.
- The Dawi. They are obsessed with the concept of revenge, as all Grudges must be answered for. This causes them to wage many unnecessary wars, which is especially stupid since they are a dying race. The fluff speaks of two dwarven lords who were fighting each other in a generation-spanning War of Grudges, even while they were being invaded by an Orc warband. The two lords eventually got together and realized that neither of them remembered what their clans were fighting over, forgave each other, and resolved to ally against the Orcs beating down on their gates. Both sides were promptly crushed by a cave-in caused by the gods themselves for failing to avenge their respective Grudges and the Orcs got to loot another Karak without difficulty.
- The Azorius from Magic: The Gathering. The guild makes so many laws that they can literally arrest ANYONE, and then justify it by finding one of the myriad of pointless laws they've passed that the individual has undoubtedly broken. They'll even arrest someone for merely thinking about breaking a law (see the card Psychic Spiral for proof.)
- The Sangheli, or Elites, from the Halo franchise. With a ridiculously rigid Bushido-style code of honor that makes the Ultramarines seem like pragmatic chaps, the Elites have often lost battles to humans they could have otherwise won, if they weren't so blindingly "honorable" (Ignoring for the minute that they had no problem turning a planet into slag.) Full frontal assaults, suicide charges, blindingly following three shady testicle-looking douchebags, and a stupid insistence on fighting the enemy fairly are all par for the course. But the most glaring example of their stupidity has to come from the fact that they consider it a dishonor to either get their own blood shed off the battlefield or become involved in a medical practice. Even Klingons aren't that stupid. The only reason they even win against the Jiralhanae (Brutes) is because the Brutes are more Stupid Evil than the Sangheli are Lawful Stupid. Well, that, and the fact that they had allied with the Humans by that point.
- The Nugganite religion, from Terry Pratchett's Monstrous Regiment: the decrees of the Borogravian god Nuggan forbid everything from the smell of beets to the color blue to babies. Many citizens of Borogravia privately acknowledge that most of Nuggan's abominations are completely ridiculous (and let the most extreme Abominations slide, because they're virtually impossible to enforce anyway), even while fretting about which Abominations they're currently committing. In the end, it's revealed that belief in Nuggan himself has dwindled, essentially leaving the god to rot away until nothing is left but a disembodied voice babbling Abominations nonstop.
- For the literature amateurs, Inspector Javert form Les Misérables. As the author himself explained: the man was built upon two simple and good precepts, namely respect of authority and refusal of rebellion; but he made those look evil in his fanatical exaggeration of them.