There's also an enormous body of federal and state law limiting an employer's ability to terminate employees for reasons having to do with race, ethnicity, religion, marital or disability status and,
The bottom line is that an employer cannot fire employees in any way that constitutes discrimination, a violation of state public policy, or contradicts any actual or implied promise regarding the criteria or procedures for employee termination. That still leaves wide latitude to fire employees for economic or performance reasons, for violating the law or internal company policies, or even for no reason at all, in some cases. Just be sure you know the law, apply your own policies consistently, and document everything when terminating an employee.