BACK IN THE Middle Ages, justice was a pretty informal commodity. In between jousting bouts, feudal lords would hang out in their fiefs, arbitrarily judging any and all disputes that may have occurred there.

Of course, that's not the American way. In this country, we have a different--though not always perfect--system, in which cases are overseen by judges, argued by lawyers and decided by juries, all bound in a complex framework of law, rights and precedent.

Except, that is, at Harvard. At this University, feudal arrangements of justice still survive in 1992--most notably in the way the College deals with charges of rape and sexual assault brought by Harvard students against their peers. By allowing--and even encouraging--students to bring these types of criminal cases to the Administrative Board, Harvard has established a private judicial system right here in Cambridge.

Like all feudal organizations, Harvard's judicial fiefdom doesn't care about its effect on neighboring areas outside its own jurisdiction--like the rest of America.

That's too bad. Because in the case of date rape, separate justice for Harvard students compromises equal justice for all Americans.

THERE'S NO question that acquaintance rape and assault is a very real problem throughout this country, and at Harvard.

A national survey of female college students, conducted by Ms. magazine in 1985, showed that one in six had suffered a rape or attempted rape in the previous year. Of those raped, 84 percent knew their attackers and 57 percent were on dates when the attack occurred.

Here at Harvard, the University's College Life Survey of 1987-88 revealed that 32 percent of undergraduate women and eight percent of undergraduate men had "experienced unwanted or inappropriate sexual attention"--though not necessarily rape or assault--from a Harvard or non-Harvard peer.

There's also no question that these crimes are extremely underreported, especially on campuses.

Only 10 percent of all rapes are reported, according to FBI victimization surveys. And for on-campus rapes, the figure drops to 4 percent, the Ms. magazine survey showed.

At Harvard, only five percent of those who had experienced "unwanted attention" reported it to College authorities.

The reason for this silence is that victims tend to blame themselves or are blamed by others--including the police, the courts, their families and their communities--for provoking the attack. This country's legal system, in short, is not too friendly to the victims of sexual assaults.

It was precisely these sorts of concerns--that date rapes were going unreported, victims unrecognized and attackers unpunished--that prompted the College to establish a Date Rape Task Force last year.

Cases of date rape and sexual assault at Harvard--as well as sexual misconduct, a less severe, non-criminal breach of Harvard's behavioral standards--are currently settled by the Ad Board, the same board that adjudicates other disciplinary and academic cases in the College. In its recently released report, the Task Force proposes measures that would improve the Ad Board's procedure for handling date rape cases.

But why, in the first place, should cases of sex crimes be heard before the Ad Board? Shouldn't these matter be settled in the courts of the Commonwealth of Massachusetts?