I still say the difference between you spraying your jeep with Krylon and me spraying water bottles, my AR-7, etc. is just a difference in quantity. I've never heard of any laws against using spray paint outside although some municipalities require photo ID while purchasing spray paint to prove you're an adult (due to taggers 20 years ago). That's another interesting irony in the SJW fight against requiring photo IDs to vote since the little darlings have to have it to get spray paint but I digress.
I can't imagine anyone complaining unless you were spraying more in the air upwind of them than you were on the car.

