1. Arizona law sucks, if it requires us to know when a felony has been committed, rather than a class "A" misdemeanor, before someone can step in and stop someone else from doing wrong, without being arrested himself. That's just plain wrong -- that's treading on the people's right to raise the ancient Anglo-Saxon hue and cry and arrest midemeanants.
The whole idea of intermediation of the law in medieval times was to interrupt the cycle of vendetta and stop people's killing one another. Now it's being used to enforce an Establishment politics of quietism and personal anomie.
2. Crashing the borders of the United States isn't a felony? You mean there is such a thing as a federal misdemeanor ?
I don't think it rises to a federal misdemeanor, but instead is some kind of administrative offense that leads directly to deportation. There are some cases where it rises to a felony level, but those are usually coupled to some other offense or prior conviction. So, given that the strong majority of illegal crossings are not felonious in nature, then the fact that someone is crossing the border does not rise to the level of probable felony.