HERE’S GOOD news for those of you heading out on the highway for the Memorial Day weekend: The average price of a gallon of regular unleaded gas in the District of Columbia has gone down four cents over the past week, to $3.85, according to the American Automobile Association. The price at the pump reflects a multitude of factors, the most important one of which by far, the world price of crude oil, is maddeningly beyond a motorist’s control. Still, the price of oil does move according to supply and demand, and apparently world market trends slightly favor D.C. drivers at the moment. Fill ’er up!

Certain D.C. politicians subscribe to a different theory, however: The gasoline market in the District market is under the predatory domination of a single man, Eyob “Joe” Mamo, who purportedly uses his ownership of about 60 percent of the 107 District stations to impose high prices. For more than three years now, populistic pols, led by D.C. Council member Mary M. Cheh (D-Ward 3), have pursued Mr. Mamo legislatively and in the courts. Their crusade has yielded nothing, which sometimes does happen to political crusades that aren’t supported by facts. And the facts are that D.C. prices (and, more specifically, prices at a handful of stations in well-to-do neighborhoods, most of them in Ward 3) are somewhat higher than those of the surrounding region — not because of one man’s perfidy but because of readily comprehensible factors such as customer demand, taxes and the size and location of individual stations.

The latest defeat for the Mamo-bashers came on May 6, in the form of D.C. Superior Court Judge Craig Iscoe’s order dismissing Attorney General Irvin B. Nathan’s price-fixing lawsuit against Mr. Mamo. In restrained but withering language, the judge chided the city’s top lawyer for trying to sue on behalf of retail gasoline dealers who are supposedly being forced to buy gasoline from Mr. Mamo at inflated prices; D.C. statutes give Mr. Nathan no such power, the judge ruled. As for the substance of the city’s complaint, Judge Iscoe practically laughed it out of court, calling the notion that Mr. Mamo’s contracts with dealers cause economic harm either to the dealers or to the general public “conclusory and unsupported by any factual allegations.”

You would think that this overwhelming defeat before an impartial arbiter would cause the D.C. government’s would-be trust-busters to reconsider. Heck, they could even seize on it as an opportunity for a face-saving retreat. No such luck. Ms. Cheh has announced that she may pursue legislation in June granting the city authority to sue Mr. Mamo. That would, indeed, answer Judge Iscoe’s procedural objections, but the city’s case would still lack a substantive basis.

How much more of the District’s limited resources do Mr. Mamo’s pursuers propose to expend on this spurious effort? We think they’ve wasted enough already.