I don't care if you quarrel. It's my company. I can change the rules in mid-stream. You're fired.
If said description is made after that time, de facto as it were, I'd run the employer through every court in the nation, and cheerfully (and win, too).
Wrongo. You're fired, and you don't get a penny. Challenge me in the courts. I'm the boss. I can change the rules anytime, for whatever reason (as long as it's not due to protected status discrimination).
Only the Regress gets to change the rules in the middle of the game, because Mr. Madison didn't think to put in a clause in the Constitution to stop them from doing so.
It's not a contract. It's employment-at-will. If I don't like you because you wear green, you're fired. If I don't like you because you cheer for the Denver Broncos, you're fired. It doesn't matter if I make that decision before you're hired, a week after you're hired, or ten years after you're hired. It's my company and my money. There's nothing you can do about it as long as being a green-wearing fan of the Denver Bronco's isn't a protected status.
There is of course the counterbalancing consideration, at minimum one of ethics as well as pragmatism.
If Joe Smith, my employee, smokes really nasty cigars at home, not on the job, and I -- the owner outright of the company -- can't stand them and the residual stench, BUT, Joe Smith also is a highly productive employee, makes me lots of dollars from his work, and I never mentioned the stench before I hired him, then I at DEAD MINIMUM am both a hypocrite and a Trotskyite to punish him in any way or form for his smoking of cigars off-site.
If he and I had agreed to this before employment, you and I have no disagreement at all. If not, well, sorry, mate, but a unilateral changing of rules in what is necessarily a bilateral arrangement is nothing more than arbitary exercise of power to dictate personal behaviour.
Suggest you look up Leon Trotsky's (David Bernstein's) writings on the subject. He's quite thorough in his descriptions of the methods of control of private behaviour.
Your company ... true. Protected by the courts? Are you willing to bet your lifesblood on it?
And even if you do win, piss enough people off and the one guy with a grudge, ability and a good baseball bat or firearm will make your children happy when they inherit.
Sometimes there's the legal thing to do, and the morally right thing to do.
Yep, the world is full of A**holes. No changing that I guess. Of course, being an A**hole isn't illegal, yet. Blackbird.