Criminal law, like other branches of U.S. law, follows a precedent system. Accordingly it attempts to provide a brake on runaway punishment for similar crimes, which may be based on popular opinion, politics, prejudice or merely the whims of a super-strict hanging judge.

The 10-year sentence handed out to Michael Milken for white-collar crimes {front-page, Nov. 21} is out of sync with the punishment given to others for similar offenses.

No one quarrels with a decision that some jail time may be appropriate in the Milken case, both as punishment and as a deterrent. But 10 years is a longer sentence than those given to some murderers, rapists, child abusers and other antisocial violent criminals. Compare, for example, Mr. Milken's sentence with the mere slaps on the wrist given to Oliver North and Adm. John Poindexter in the Iran-contra case.

I don't quarrel with the established principle of our criminal justice system that the poor should be penalized no more severely than the rich. However, in the Milken case it appears that the reverse has happened. Mr. Milken has been unjustly singled out for excessive punishment because he is rich rather than poor.

It seems that a young and relatively inexperienced U.S. district judge, Kimba Wood, has decided to ignore established sentencing precedents and substitute personal judgment for many years of prior judicial wisdom. ALFRED B. LEVINE Chevy Chase