Question: When I see inconsiderate drivers parking at lots reserved for the handicapped, I consider reporting their cars. If they get fined, will I have negative karma?
Answer: If you will create negative karma for doing so, all parking attendants will receive negative karma for issuing summons for illegal parking too, simply for doing their job, for the welfare of society. Of course, this is not true – especially if your intention is good – for the benefit of the handicapped, and even the inconsiderate drivers, so that they will not create more negative karma by depriving the needy of spaces in future. This is compassion for all parties.
Question: If the drivers have good reasons for parking there, will I have negative karma? Or should I just let them be?
Answer: We should just do good with the best of intentions and judgements, and not always do nothing (or something rash) due to uncertainties. Society is improved by the proactive. Alternatively, you can leave a note written with good will on the windscreen, to inform the drivers that their cars will be reported in future, if still parked there. Explain that just as they would not wish to be deprived of their deserved spaces, the needy would not wish so too.