As far as it goes, the tough new weapon being used in the war against drugs is fine. But it doesn't go quite far enough.

Federal law allows agents of the U.S. Customs Service to search vehicles at border crossings. Until recently, vehicle-forfeiture provisions were applied only to obvious drug dealers. But under a new program called "Zero Tolerance," anyone caught with even one marijuana cigarette can lose his or her automobile.Only this week, the $2.5 million yacht Ark Royal was briefly seized by the government because a small amount of marijuana was found on board.

In another case, Scripps Howard News Service reports, the driver of a Porsche coming in from Canada lost his car because a passenger had marijuana in his pocket. In still another instance, an airline stewardess' car was seized because her boyfriend was carrying a small quantity of marijuana. The drivers complained that they didn't even know their passengers had the illegal substances.

While owners can pursue legal procedures to get their cars and boats back, seizures stand in most cases. The cars and boats later are sold by the government and the proceeds go into the Custom Service's budget.

While the new program may seem harsh, it makes sense. As officials of foreign countries where drugs originate constantly point out, there would be no drug smuggling if there were no market in the United States.

Those users whose cars are being confiscated under the "Zero Tolerance" program are part of the market for drugs from Colombia, Mexico, and other places. They are among those whom First Lady Nancy Reagan recently accused of being "accomplices" to the large number of murders endemic to narcotics trafficking.

So far, so good. But authorities ought to extend the forfeiture policy beyond the borders and into the interior of the U.S. Federal law permits the confiscation of property used in drug transactions anywhere in the country. When police observe someone in a car buying drugs from a seller on the street, they have a right to seize the buyer's vehicle because it is being used in the transaction - and they ought to exercise that right.

The loss of a car just might make a drug user wonder whether a brief "high" is worth the price. If it takes stern measures to get more Americans to "just say no" to drugs, so be it.