The law system was poorly thought out and built to spite you anyway.
For one, the AI didn't need to follow the law. It would break the law and get yellow carded, which didn't matter as it's not like the AI needs to atone for it's actions anyhow. There's also characters that have ribbons, which are items that are explicitly "I can break the rules whenever I want" items. Of course, you can never get one of these ribbons, and while there IS a special character that allows you to bypass any law, you can only get him AFTER you've pretty much beaten every mission anyhow. How useless.
Secondly, there are items that can change the laws mid-battle. Two, actually, there are those that can erase the law for the battle, or add a new one. The 'add' items are completely useless, as you'd only want to use them to hinder your opponents, but they aren't effected by the law anyhow, so you'd only want the 'anti-laws' in order to free yourself from the constrictions of laws anyhow.
thirdly, some of the laws were ABSURD! There's one law that says, get this, you're not allowed to fight. Hey! This is a BATTLE! Why am I not allowed to FIGHT?! Yep, if anyone does damage to anyone else, that's an infraction of the law, and since the AI doesn't need to follow the law...
FOURTHLY, if you were carded, you'd be penalized after the battle in some way. One of the penalties is that the offending unit would have one of their stats REDUCED PERMANENTLY! For perfectionists, this is UNFORGIVABLE. If you want an ideal character, you pretty much have to reset the game right there and do the battle again. Hope you saved recently!
On an unrelated note, I hated FFTA because it doesn't have multiplayer, so even though you can make your parties ridiculously powerful, you can never fight your friends to show off, or compete in any way. How utterly pathetic.