Justice Department officials are encouraging federal, state and local prosecution of drug users as an effective way to reduce demand for cocaine, marijuana and other illegal substances. Among the efforts being touted by department officials: _A border-crossing drug arrest program spearheaded by the U.S. attorney's office in San Diego, Calif., is resulting in 10 to 20 drug-carrying motorists a week being arrested by U.S. Customs Service agents and charged with possession under federal drug laws. _A recently enacted New Jersey law revokes the licenses of drivers arrested with drugs in their cars. Also their cars are confiscated and they must perform at least 100 hours of public service work in addition to facing possible conviction for possession, which carries a jail term and a fine. The National Drug Policy Board, a Cabinet-level group chaired by Attorney General Edwin Meese III, Thursday approved a plan under which authorities will arrest and prosecute anyone caught entering the country with illegal drugs, no matter how small the amount. The idea of cracking down on users isn't a new one at the federal level. It has been included in previous Reagan administration anti-drug strategies. But the renewed emphasis on it is recognition that ``we need to focus on the demand for drugs,'' a Justice Department official said last week, speaking on condition of anonymity. ``We're going to hammer this thing into specific ideas and programs.'' Arresting users at the federal level isn't expected to take up a significant portion of resources because they will be ``picked off the fringes'' of cocaine dealing operations and major drug distribution rings already under investigation, says Assistant Attorney General William Weld, head of the Justice Department's criminal division. Weld said the approach will reinforce the point that ``there's no such thing as recreational drug use.'' The border-crossing drug-arrest program in San Diego being pushed by U.S. Attorney Peter Nunez caught 900 people last year, most of whom were permitted to plead guilty to a misdemeanor. They avoided jail time but paid steep fines and many of them were first offenders now saddled with criminal records. ``I think demand for drugs is the problem, not supply,'' says Peter Nunez, the U.S. attorney in San Diego. ``We're trying to figure out a way to get the message across to the users that they are the problem and there are adverse consequences.'' Justice Department officials regard some of the demand-side programs in place in New Jersey under a recently enacted anti-drug law as models that ought to be duplicated elsewhere. A New Jersey drug prevention education fund is financed with drug users' fines. Dealers get extra prison time for selling near schools. And the law's provisions yanking licenses and confiscating cars of those in possession of drugs strikes terror in the hearts of high school students. New Jersey Attorney General Cary Edwards says students' eyes glaze over when he warns them they could go to jail for drug use, an unlikely outcome for young first offenders. But they snap to attention when he tells them they won't be able to drive. ``We have to teach the marginal users not to be users any way we can,'' says Edwards. ``If society believes that law enforcement can stop drug distribution, they're crazy. We have to dry the market up.''