Be it in relation to DWI or another criminal offense, an idea has to run the gauntlet called the North Carolina legislative system before it becomes law. After a state law has been passed, cities gain the power to enforce it on their own terms—as long as enforcement doesn't come into conflict with the law itself.
The process of creating laws at the state level is relatively the same as how the federal government does so: draft a bill, read it, get it approved in committee, read it some more, adopt it, submit it to the head honcho, and get it signed. This is, of course, an oversimplification of a legislative Rube Goldberg machine, but this is the basic idea.
What most people don’t know is that many laws are born from the ideas of private citizens or groups. According to the General Assembly's nifty flowchart, some laws start as the brainchild of a concerned citizen or group's mind. Mothers Against Drunk Driving (MADD), for instance, pioneered DWI legislation in various states in part by using a popular writer's death to justify the initiative.
That writer was Margaret Mitchell, the woman behind Gone With The Wind. In 1949, as she was crossing a street with her husband in Atlanta, a taxi driver named Hugh Gravitt struck Mitchell by accident while driving impaired. Mitchell was the first DWI fatality to have made the front pages. You don’t have to be a lawmaker to change the law – you just have to have the right idea.