It's clear that these bots hurt poker players, which is why online poker companies work so hard to get rid of them. But they're not actually breaking the law. They're just being evil, which isn't in and of itself illegal.
Using a poker bot is a way to utilise software instead of an actual player. In most cases, this is cheating and not accepted by most legitimate poker sites. There is some debate about the level of computer assistance a player can legitimately use while playing.