There isn't a federal law that covers stuff like this. We really only have employment discrimination laws at a federal level (i.e. you can't fire someone for b

There isn't a federal law that covers stuff like this. We really only have employment discrimination laws at a federal level (i.e. you can't fire someone for being a certain race, religion, etc.). So it's up to each state and local area to define employment laws and it varies a ton. In some states they have 'at will' employment laws that effectively say you can be fired for any reason and with or without any notice. I imagine rescinding offers fall under this and are perfectly legal in some areas.