Ok so we all know that Bloodbending is a form of bending that is illegal but hears a quastion, is bloodbending the only bending art that's outlawed. Are thier other bending arts that are aganst the law in the United Republic of Nations?
I mean, any bending used violently is technically illegal, but unless done publically you really couldn't be prosecuted for it (hence Tarlock). I guess I could see lavabending being outlawed totally though because of how exceedingly destructive it is (as if throwing around fire and lighting isn't).
I'd guess that Rare Scary Stuff™ like lavabending or combustionbending could get you into trouble if you did it, say, within city limits for any reason other than immediate self-defense. And even if it were immediate self-defense, you'd likely get slapped with a fine for melted streets or damaged buildings.
Not to be too cynical, but: if the perp had considerably more influence, the victim might very well get slapped with collateral-damage fines for defending themself. (Heaven only knows shit like that happens in real life).
Assuming no government corruption is involved, I don't think we have reason to think that anything else would be illegal per se, but reckless use would be illegal. So you can't just earthbend the parking lot whenever you want, & you can't go shooting lightning every which way with no consequences.