Like Dzug, I'm guessing that this question might come from the USA.
This is a UK-based site, so the answers you'll get here will be based upon UK law (or, more accurately, on the laws of England & Wales) unless we have reason to know that the question originates from elsewhere.
In case this question comes from
England or Wales, I'll give the appropriate answers:
1. It's not an offence to be in possession of an open alcohol container in a public place. Local authorities have the power to create 'Alcohol Designated Areas'. (They only do this when there are specific problems, related to drinking, in those areas). It's still not an offence to be in possession of an open alcohol container, or to be drinking from it, in such an area. However, it is an offence within such an area, to fail to stop drinking or to fail to hand over the container, if required to do so by a police officer.
2. A car isn't a 'public place'. (Even a taxi wouldn't qualify as a public place, although it's arguable that a bus might).
3. It's not an offence to have an open container of alcohol in a car.
Now let's assume that you're in the
USA:
A. I would find it hard to believe that any laws could define the inside of someone's own vehicle as a 'public place'. That would seem to make a mockery of the English language - although most Brits think that Americans do that anyway ;-)
B. Quote:
"Federal law requires states to enact and enforce a law prohibiting any driver or passenger in a motor vehicle on a public highway or road shoulder from possessing an open alcoholic beverage container or consuming alcohol anywhere in the passenger area".
Source:
http://www.cga.ct.gov/2005/rpt/2005-R-0152.htm
Chris