I would assume it's illegal because of vapors from acetone.
edit: maybe not, IDK "Exposure can occur if you live near a landfill site that contains acetone, near busy roads, or near other facilities such as incinerators that release acetone emissions."
http://toxtown.nlm.nih.gov/text_version/chemicals.php?id=1
I work with acetone all day though, and it's kind of nasty stuff. It is flammable, so it might be more dangerous for accidents. There was a mythbusters about blowing up a gas tank, and they decided it was just too hard to get the right vapor levels. Perhaps with this, it would be very easy for a car explosion?