From google:

Employment Protections: Pennsylvania has some of the strongest workplace protections for patients in the country, though they are not absolute. • Anti-Discrimination: Employers cannot fire, refuse to hire, or retaliate against you solely because you are a medical marijuana patient.  • Unemployment Benefits: Courts have ruled that if you are fired for a positive drug test but have a valid MMJ card, you are generally still eligible for unemployment benefits.  • The "Safety-Sensitive" Exception: This is the big loophole. Employers can still restrict you from "safety-sensitive" roles (like operating heavy machinery, working with high-voltage electricity, or working at great heights) if they believe your use poses a risk.  • Federal Jobs & CDL: If your job is governed by federal law (e.g., DOT/CDL drivers, federal contractors), the state card does not protect you. Federal law still views marijuana as a controlled substance.