Driving in this country is a privilege. Driving while intoxicated is also a privilege, at least for now.
In most states it is illegal to drive with a blood alcohol content or BAC of .08% or higher. This is down from .10% quite a few years back. There is a current movement to lower it even further to .05%.
In some states it is illegal even if you are under .08% BAC but are showing signs of unsafe driving due to alcohol. This makes sense. If someone is not driving safely then they should be pull