Working Conditions and Benefits

... An at-will employee can be fired at any time, for any reason (except for a few illegal reasons, spelled out below). If the employer decides to let you go, that's the end of your job--and you have very limited legal rights to fight your termination......Even if you are an at-will employee, you still cannot be fired for reasons that are illegal under state and federal law. In these situations, the government has decided to make an exception to the general rule of at-will employment.
For example, if your employer is subject to federal and state laws prohibiting job discrimination (as all but the smallest employers are), you cannot be fired because of certain characteristics, such as your race, religion, or gender. (For more information on discrimination, see Your Rights Against Discrimination and Harassment.) Similarly, you cannot be fired because you have complained about illegal activity, about discrimination or harassment, or about health and safety violations in the workplace (see Nolo's article Assert Your Safety Rights Without Fear of Retaliation). And you cannot be fired for exercising a variety of legal rights, including the right to take family and medical leave, to take leave to serve in the military, or to take time off work to vote or serve on a jury...

...Many people are surprised to learn, whether from an employment contract or employee handbook, that they are an "at-will employee". But what does being an at-will employee mean? Being an at-will employee means that your employer can terminate your employment at any time, for any cause - with or without notice. An employer has every right to walk up to an at-will employee and say, "I don't like that your favorite color is purple. You're fired." There are very few, if any, remedies for you, unless your employer did something to violate your employee rights or broke labor laws....

...In general, if the reason for termination is not because of discrimination on these bases, or because of the employee's protected status as a whistleblower, or because they were involved in a complaint filed under one of the laws enforced by the Department of Labor (see Whistleblower and Non-Retaliation Protections), then the termination is subject only to any private contract between the employer and employee or a labor contract between the employer and those covered by the labor contract....