My original question was whether or not Airbnb would support and enforce the fine for smoking. I may have missed it but did anyone answer that question?
As to the other respondents' opinions I offer the following:
The guests smoked inside and outside of the house. The security camera is plainly visible to anyone entering the property.
It captured them lighting up and then entering the house. It does not capture activity in the house.
There are security cameras at the entrances to just about every hotel in the city of Seattle and most of the block I live on is monitored by private security cameras. That's the way it is in 2016.
I request that my guests do not smoke near my neighbors' homes. If my guests did smoke near my neighbors' homes my neighbors would be bothered by my hosting.
Smoking near my neighbors' houses is a legal but noxious act. I request that my guests not do it and that request is part of the house rules. I wouldn't attempt to fine someone for smoking near my neighbors but if I heard about it I would ask that the guest not do it again and if the guest did do it again I would terminate the stay.
Many actions are not illegal but still totally unwelcome.
I could go on and on with examples of legal but unwelcome acts that might cause someone to regret hosting a certain guest:
Spending hours repairing a crummy car with the hood open and tools on the sidewalk, bringing several cars to use on-street parking, inviting dozens of friends to meet on the street corner in front of the property, leading a workout class complete with push-ups and burpees on the sidewalk, organizing a protest and exercising one's First Amendment rights to free speech, posting politically oriented signs, sunbathing on the sidewalk, performing personal grooming on the sidewalk, talking loudly on the telephone for long periods of time in front of the neighbors, asking neighbors weird questions, knocking on multiple neighbors' doors to inquire if their homes are for sale...
Some of those things might be welcome in certain neighborhoods but not in others. Certain neighborhoods might really appreciate sunbathers, some neighbors might like hearing new lively music, some might hate it.
Being a good guest means being respectful of the area where you are staying.
Get the point? there are things that are legal but still really obnoxious in certain areas. In this area, smoking is one of those things.