I doubt federal courts would want to start a string of precedence of employees being fired because... say for example they would willing violate an OSHA statute...
There are many other ways employees are protected from being forced to break safety regulations or force termination.
E.g., AIR21
(49 U.S.C. §42121) provides whistleblower protection status.
If a company is pressuring pilots to violate FARs and compromise air carrier safety, it may be advisable for a pilot to contact a lawyer (through a union if applicable) and immediately report such conduct to the FAA. The pilot will be protected under AIR21 against any retaliation (including termination).