THE REMOVAL of diplomats from the coils of local justice is an ancient and honorable practice designed to ensure that they are not arbitrarily fettered in their essential work. At the same time, as Washingtonians have all too often been reminded, the practice lends itself to abuse. In the most recent instance, a son of the Brazilian ambassador was arrested for allegedly shooting an employee of a Wisconsin Avenue bar. The charge against him was dismissed because, as a member of the household family of a diplomat, he is immune from prosecution. The victim is recovering at Georgetown Hospital.

Privileges like diplomatic immunity are not extended lightly and cannot be withdrawn or abridged lightly. The United States, which dispatches diplomats to a great many countries where the local law is an arbitrary thing, has a greater interest than most in preserving its integrity. Revolutionary Iran's withdrawal of immunity from the American diplomatic corps in 1979 stigmatized that regime around the world.

Still, abuses of immunity cannot simply be met with a shrug. The same international treaty that spells out the privilege of diplomatic immunity specifies that those receiving it have a duty to respect local law. Although the law cannot be applied to them, the State Department has available a range of diplomatic and administrative alternatives, including turning up the political heat and warning or even expelling the offender. A few years ago, in response to the latest incident in the especially egregious category of auto violations, Congress passed a law requiring diplomats to carry auto insurance and insurers to pay up if negligence were found.

No similar requirement covers gun victims. For mishaps in which local citizens have been deprived of the usual remedies of the law, however, responsible embassies, including American embassies abroad, have usually found ways to make financial and other amends. In Washington, the State Department's protocol office stands ready to mediate citizen complaints.

No one wishes to embarrass the Brazilians. But what the young Brazilian was (briefly) accused of was a flagrant offense not only against American order but also against American hospitality. Immunity was not invented and is not sustained to let diplomats and their families flout the law.