MOST WASHINGTONIANS who would never drive drunk nonetheless wouldn't refrain from driving home after a leisurely dinner that included a single glass of wine. Perhaps they should -- and not because they represent an intolerable menace on the roads. As Post staff writer Brigid Schulte reported, Debra Bolton had a glass of red wine with dinner back in May and started driving home -- for which she was arrested and spent months fighting a charge of driving under the influence of alcohol. Ms. Bolton's blood alcohol level was .03, significantly below the legal limit of .08. But under the District's exceptionally tough drunk-driving laws, you can actually face charges for any measurable blood alcohol level. You don't, in other words, have to be drunk to be charged with drunken driving.

All states now set .08 as the legal limit, and it isn't uncommon for states to allow DUI prosecutions for blood alcohol levels below that in cases in which a driver behaves dangerously and shows other signs of impairment. This makes sense, since alcohol impairs people to different degrees. But Washington's laws are particularly stern. In Maryland and Virginia, for example, the law presumes that a driver is not intoxicated if his or her test measures below .05. In Washington, however, there is a presumption of impairment above .05, but no presumption one way or another below, even for very low readings such as Ms. Bolton's. That puts a huge amount of discretion in the hands of police officers. Ms. Bolton, for example, was stopped for driving at night with her headlights off. Unlike many others, who choose not to fight their cases but avoid criminal prosecution by agreeing to counseling, she hired a lawyer and ultimately prevailed.

We're all for coming down hard on drunken driving, a terrible problem that kills a great many people around the country. Vigorous enforcement and tough penalties, particularly for repeat offenders, save lives. But as with so many areas, the lure of "zero tolerance" quickly leads to absurdities. There has to be some blood alcohol level below which a driver is presumed to be unimpaired. If people below that level are driving badly, they deserve a ticket for the infraction. But they shouldn't be arrested for driving under the influence.