Employment at Will means an employer has the right to fire (or discipline or promote) an employee for a good reason, a bad reason, or no reason at all, so long as it is not an illegal reason.
What are illegal reasons? It depends on the federal and state law, but here are some:
- Breach of a contract (express, implied, written or oral, depending on your state's law);
- Violation of a discrimination statute (federal, state or local) based on race, color, sex, national origin, religion, age, disability, veterans' status, disabled veterans' status, union affiliation, and other reasons.
- Because of the employee's lawful off-duty contact, lawful expression of first amendment rights, lawful on-duty conduct; and/or in retaliation for exercising any of these rights.
Check your local statutes to be sure. In addition, do not forget that many states require employers to give employees written notice of termination and a statement of the reasons for the termination.
Source: Epstein, Becker & Green, November 10, 1998, New York