First, a mandate is NOT a law.
Second, record everything if you want to instigate legal action, but here's the gist.
You don't have to wear the mask. You are exempt. If they ask you why you are exempt, you can simply tell them for medical reasons. If they ask you you're medical reasons, you CAN SUE due to the HIPAA (Health Insurance Portability and Accountability Act of 1996). If they discriminate against you and ask you to leave or accept service outside or some faggy shit, you can get them fined for discrimination. Its a $75,000 fine in my state.
EDIT: If you get into some sort of confrontation, be sure to ASSERTIVELY inform them of your rights. NO PUSSYFOOTING AROUND. WE ARE DEALING WITH SATANISTS AND PSYCHOPATHS. Being loud may help to inform other sheeple to do the same and flex their own rights. After you have filmed the encounter, be sure to upload to bit chute, gab, or rumble and spread the cure for mask tyranny.
This is what I’ve been doing as well deep in a blue hell. Look them in the eyes and firmly say “I have a medical exemption.” Most times the pimply teenager won’t say anything.
Did have a black disabled vet (customer) cuss me out in target for not wearing a mask. His internal processing short circuited when a target employee told him they aren’t enforcing it... because it’s not a law. Looking back, kind of endearing this dude fought for our country without knowing his rights.
You LEGALLY don't have to tell them your "medically" exempt. You should only tell them you are exempt... If you start divulging medical info, it sounds like you are voluntarily breaking the HIPAA. My father fought in the Korean War, and if a fucking Chinese shill told him to wear a commie mask over here he would probably shoot the fucking spy.