Narrative:

At the gate in ZZZ; almost ready for door closure and gate departure when we get a lavatory smoke warning. I called back to the aft cabin flight attendants and they tell me a passenger just exited one of the aft lavs and a cloud of smoke followed him. When confronted; the passenger denied smoking or vaping; and claimed the smoke was present before he entered the lavatory.I called for a customer service manager to come remove the passenger; and the manager; after talking with the passenger; informed me that he still denied smoking and that he was refusing to leave the airplane.after conferring with the manager and his supervisor; and confirming events with the aft cabin flight attendants; I decided to have the entire plane disembark and re-board without the offending passenger.as passengers were deplaning; the suspected smoker stopped at the L1 door and demanded his money back. From the cockpit; I instructed this gentleman to leave my airplane. He refused and was belligerent. I closed the cockpit door and called for law enforcement. After everyone deplaned; we re-boarded and left for ZZZ1.in the current economic/pandemic environment; the airline has been force to offer really low fares. I feel this means some of our passengers are not frequent flyers and may not understand what's expected of them.I feel like the customer service manager initially was reluctant to have the passenger removed; due to the passenger claiming he hadn't smoked in the lavatory. The aft cabin flight attendants saw him step in the lavatory just prior to the smoke alarm being triggered. After I continued to advocate for his removal; the customer service team did as I requested. I'm not sure what was initially said to the suspected smoker; but when safety is involved; there shouldn't be an option of letting the passenger remain onboard.

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Original NASA ASRS Text

Title: Air carrier Captain reported that prior to gate departure a lavatory smoke warning occurred. The passenger allegedly smoking in the lav refused to leave and was ordered off by the Captain.

Narrative: At the gate in ZZZ; almost ready for door closure and gate departure when we get a Lavatory Smoke warning. I called back to the aft cabin flight attendants and they tell me a passenger just exited one of the aft lavs and a cloud of smoke followed him. When confronted; the passenger denied smoking or vaping; and claimed the smoke was present before he entered the lavatory.I called for a customer service manager to come remove the passenger; and the manager; after talking with the passenger; informed me that he still denied smoking and that he was refusing to leave the airplane.After conferring with the manager and his supervisor; and confirming events with the aft cabin flight attendants; I decided to have the entire plane disembark and re-board without the offending passenger.As passengers were deplaning; the suspected smoker stopped at the L1 door and demanded his money back. From the cockpit; I instructed this gentleman to leave my airplane. He refused and was belligerent. I closed the cockpit door and called for law enforcement. After everyone deplaned; we re-boarded and left for ZZZ1.In the current economic/pandemic environment; the airline has been force to offer really low fares. I feel this means some of our passengers are not frequent flyers and may not understand what's expected of them.I feel like the customer service manager initially was reluctant to have the passenger removed; due to the passenger claiming he hadn't smoked in the lavatory. The aft cabin flight attendants saw him step in the lavatory just prior to the smoke alarm being triggered. After I continued to advocate for his removal; the customer service team did as I requested. I'm not sure what was initially said to the suspected smoker; but when safety is involved; there shouldn't be an option of letting the passenger remain onboard.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.