IN 1981, Thomas E. Dorsey was convicted on a charge of manufacturing PCP. He was paroled in late 1986 and soon arrested and convicted again on the same charge -- manufacturing PCP, enough to sell for $1 milllion on the street. But the penalty was much more severe this time. Mr. Dorsey, who was sentenced Tuesday, won't be a free man again for a very long time.

That is the result of a 1986 law that provides stiff mandatory minimum sentences for repeat drug offenders. U.S. District Court Judge John Garrett Penn sentenced Mr. Dorsey to 45 years in prison without parole. Mr. Dorsey can earn no more than 56 days per year for good behavior. He will spend at least 37 years in jail. That was the stiffest sentence ever imposed here on a drug defendant. Was it appropriate? The answer is yes.

Repeat drug offenders here have been back on the streets too soon and quickly return to drug trafficking. Because the drug trade is so lucrative, many dealers have felt it worth the risk. That ratio of risk to seeming benefit has also trapped others who might have avoided illicit drugs. The relatively quick release of offenders was damaging to the morale of the police officers and investigators who made the arrests.

PCP is one of the most deadly drugs available today. It is inexpensive and its use among youths here is widespread. A PCP "high" can result in irreparable brain damage, and it often causes users to commit violent acts. PCP users here have been responsible for a number of particularly brutal crimes. Statistics compiled by the D.C. Pretrial Services Agency for the month of October showed that 45 percent of those arrested on criminal charges in the District tested positive for PCP use.

Another point can be made here. For the past several months, in Operation Clean Sweep, thousands of arrests have been made by saturating illicit-drug areas with police officers. The operation's effectiveness has been questioned because many of those arrested were quickly back on the street, pending trial, and arrested again. Those multiple arrests will be viewed differently when a law that mandates longer prison sentences for repeat offenders is applied. A much stronger deterrent, in the form of stiffer sentences, was badly needed. The new law -- and Judge Penn's use of it -- sends the right message.