Firing someone because they didnt obey your order to break the law is not duress?

It’s not at all obvious that going to work in a factory that’s operating against a county order is breaking the law.

The county order prohibits both businesses operating and individuals engaging in out-of-home activity except as explicitly permitted by the order, and violating a county public health order is a crime (misdemeanor) punishable by up jail.

Automobile manufacturing is not one of the listed exceptions, so it is illegal both to operate (for the owner) and to go to work at (for the employees) such a business.

It's not at all obvious that it's not, either. At the very least, it's against the spirit of the order.

You’re begging the question that there is a law to break.