[hannasanarion]

Yeah, company contracts can add their own restrictions on top of at-will, and so can state laws.

In 42 states, you can't fire someone for acting in a way that's compliant with public policy, like for saying "I won't ship these defective airplane parts".

36 states have an "implied contract" exception, meaning that if you've informally written or said that you won't quit or fire without good reason, then you can be bound by that as if it were a contract.

11 states have "good faith" exemptions, meaning you can't fire for mean or selfish reasons, like to avoid paying retirement benefits.