I don't know if the safety standards for human and animal food crops are different or equivalent. Also, if they are different, by what magnitude do the limits for toxins and the like differ?
As for laws, this is for Germany/Europe
What is animal feed in one country is human food in another (E.g. "Polenta") but that's just one example, so:
However, that is just some and most and probably and the quality control between maize for animal consumption and maize used for human consumption is different, so the quality of the food you'll be cooking out of chicken feed will be much lower than the one rated for human consumption.
I mean: I once made a stew out of dog food by adding pepper, allspice, nutmeg and some nice dark monk beer, but that was a drunken bet and the two other drunks absolutely loved it the night itself until we realised the next day it was mostly horse meat...