When it comes to movie stars, I subscribe to the Ronald Reagan Rule. Reagan used to tell his aide Michael Deaver that if you liked someone on the screen, chances are you would like them in person, too. That's one reason why I think the imprisonment of Robert Downey Jr. is an outrage. From what I've seen on the screen, I think he's a nice guy.

As it happens, the record supports me (and Reagan) on this one. If Downey ever committed a violent crime, it hasn't been mentioned in the press. If he ever held up anyone, mugged an old man or even sold drugs, it has never been reported. What he did is violate his probation after pleading guilty three years ago to drug possession and having a concealed weapon in his car. He can't stay clean -- and for that he's going to jail. The judge gave him three years.

Some time ago, Downey lost control of his life. Fix by fix, he has been going about the process of dismantling it. He has lost his wife, his child -- and now his livelihood and freedom. He should be in a hospital. He should be receiving treatment. He is not, as you and I know the term, a criminal. What is he doing in jail?

In fairness to the judge, Lawrence Mira, Downey has been in six drug treatment programs -- and flunked them all. He violated parole three times by failing to submit to drug testing, although this time around, Downey said he was determined to remain drug free. The judge, in effect, scoffed -- and who can blame him? He pronounced Downey a danger to himself and sent him to the slammer.

"We tried rehabilitation and it simply hasn't worked," Mira said.

Yes. But what other addiction is punishable by jail? We don't send alcoholics to prison unless they kill someone. And yet about 28,000 people die annually from cirrhosis of the liver and 17,000 more people are killed in alcohol-related traffic accidents. Some 14 million Americans suffer from alcohol abuse or alcoholism (compared with 3.3 million hard-core drug users) and we all know what damage they can do. When, though, was an alcoholic imprisoned for three years merely for being unable to stay sober?

In his recent book, "The Fix," Michael Massing argues for a return to the Nixon-era drug policy in which treatment, not incarceration, was emphasized. That policy, not wholly effective and not as telegenic as drug busts, has since been deemphasized. The government's drug budget of about $17 billion is mostly spent to control supply -- not, as Massing calls it, "demand." The "demand" side, the addicts themselves, is often shortchanged.

No one can write the phrase "war on drugs" without following it with the word "failure." We are engaged in a nasty little drug war in Colombia. We imprison people for using marijuana for medicinal purposes. Our prisons hold 300,000 drug offenders (many for mere possession) and the federal government alone spends some $2 billion annually just to house them. We are doing something wrong.

The fact remains we do not quite know how to do this thing right. The drug problem is infinitely more complicated than it was during the Nixon era -- more kinds of drugs, greater potency. Treatment programs are very expensive and they don't always work. Maybe, as with alcohol and alcoholism, we are just going to have to live with the problem.

Still, it only makes matters worse to treat a public health problem as a crime. As Massing points out, the nation's so-called drug czars have all lacked "even rudimentary experience in treatment, prevention and epidemiology of drug abuse." They have been former cops, former military officers or, as with William Bennett, current moralists. They know what's wrong.

But the problem is not the purported immorality of the occasional user or the marijuana smoker, but the addict and the social wreckage he does. This is the sort of person who needs treatment, not jail -- although his dealer is a different story altogether. Both the criminal justice and the public health approaches are valid. We just have to get the proportions right: Treat addicts, imprison dealers and decriminalize drugs such as marijuana. As with alcohol, most people can use it with impunity.

Downey is a statistical oddity. Most hard-core users are poor, often minority group members. But he serves a purpose. Because of his celebrity, this smiling actor, this sweet man who appropriately played Charlie Chaplin, can personify the absurdity and cruelty of our national drug policy. He's gone to prison -- a criminal whose only victim is himself.