Date: 202101
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Other Preflight briefing
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Distraction; Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Passenger Misconduct
Detector: Person Flight Attendant; Person Flight Crew
When detected: Pre-flight
Result: General None Reported / Taken
Contributing factors: Company Policy; Human Factors; Environment - Non Weather Related
Primary problem: Environment - Non Weather Related

Narrative: Aircraft X had to return to ZZZ for an electrical problem. On the ground after landing; I learned from the flight attendants that there had been a problem with a passenger. They initially described it as a medical issue; saying prior to departure the CSR had struggled to evaluate if he was fit to fly and eventually decided he was. I was told he was the last passenger to board. There were issues with him not wearing his mask properly and several crew members had asked him to cover his nose. He was seated in the wrong seat prior to departure. At one point he was coughing/hacking severely to the point where other passengers began to react with concern. On the return back to ZZZ; two flight attendants said he was unresponsive when they asked him to put his seat and tray table upright. They said they had to resort to physically shaking him before he responded; They asked him if he knew his name and where he was going and he either would not or could not provide this information; but eventually just said he was 'going home.'When he was pointed out to me in the terminal prior to the 'second' flight; on a new aircraft; and his mask was down below his nose. The flight attendants were very concerned and did not want him on our flight because he would not obey crew member instructions. I agreed the situation would likely not improve once airborne and did not want to risk yet another diversion if that it indeed turned out to be the case and therefore told Customer Service not to board the passenger.I told one CSR he would not be allowed on the flight. As we prepared the new aircraft for departure I was confronted by yet another CSR Supervisor who again tried to talk me into taking him. 'We're out of options. There are no more flights out. He's crying. He's very nice. He just wants to go home.' I was moved; but the unruly passengers are always nice to the agents when they're on the ground trying to make up for bad behavior and I had to remember that every Flight Attendant in the back; to a person; had an issue with this passenger and did not feel comfortable taking him. I stood my ground.  The FAA adopted a Zero Tolerance policy earlier this month. I am disappointed in our lack of training and or communication of FAA regulations to pertinent front-line employees.




Synopsis: Air carrier Captain reported a passenger was not compliant with face mask policy.