Rest assured, if they really wanted to, they could have found a legal way to rescind the offer. And neither "retribution" nor what you probably meant to say, "retaliation" applies here even if they do fire you shortly after hire.
If they actually do fire you and you have reason to believe it is illegal discrimination, there will be plenty of time to deal with it then. There's really no point to trying to figure out all the possible laws that might apply regarding a termination that hasn't happened.

