Thanks JB for your quality response. I really appreciate it.

The context here is I was fired with no warnings or verbal reprimands, nor had I ever received any for anything else, by mentioning that fatigue may be an issue for me soon. The context is I was under formal treatment by a licensed physician for hypertension and acute sinusitis at the time, and was in fact taking prescribed drugs daily. It was a real health issue, not a trick or negotiation tactic. I told dispatch about it and they immediately escalated to management who apparently took it as a tactic or threat and fired me on the spot. No warning, no verbal, nothing. There had been no prior issues with this subject (or any fireable-offense sort of subject) either. I did not see it coming and was stunned. I thought I was doing the right thing by telling them about my impending health issues but boy did that backfire. Pilots, do not discuss anything with dispatch. Do not tell them anything.

Ok fine, fast forward. Now my employer is saying I did or could not have had a legal basis for refusing to fly if I were sick. I think (know) they are wrong. Certainly no company wants its pilots fatiguing out. I get that. But if you must, there has to be some legal basis for it.

But I think I have my answer. FAR 91.13 indicates you are liable as pilot if you operate an aircraft recklessly, for example knowing you have a an unfit condition for a flight. Next, FAR 61.61.53 "Prohibition on operations during medical deficiency" indicates that it is illegal to fly if you do not meet the conditions of your medical issuance. I think those are the laws I am looking for. I am looking for laws saying that if I know of any condition that makes me unfit then I have a legal obligation to not fly. I think it is pretty clear that these laws supporting that sort of decision. Whether you get fired or not is another subject. If you work for this firm you will be fired ruthlessly it seems.