FOREVER, it seems, a little plantation has existed on Capitol Hill. Sen. Patrick Leahy calls it the last plantation in America. It's the Senate cafeteria, whose 230-plus mostly black and Hispanic workers are denied by their senatorial employers the right to unionize--a right those same senators would not dream of trying to deny to people in the same line of work, or almost any other, elsewhere in America. In their frustration, the cafeteria employees have even petitioned the International Labor Organization, the United Nations agency that helps officially squashed labor unions, like Poland's Solidarity, try to regain their rights.

The rationale cited in defense of the Senate's practice is, as you might imagine, constitutional: the separation of powers. It is said that Congress cannot permit a group of its workers to be covered under the Civil Service Reform Act, the basic law that allows federal workers to organize unions and bargain with the government, because then the executive branch would be policing the legislative branch. How many senators would care to stand up in public and render such a fancy and unpersuasive alibi for denying people their basic rights?

Anyway, the Library of Congress, also part of the legislative branch, is unionized. So are the Government Printing Office and the General Accounting Office. Does anyone doubt that the reason the cafeteria employees are singled out arises from the very unhappy tradition of disrespect for this group long evident on the Hill?

But what was most revealing about The Post's update of the cafeteria workers' plight yesterday was an accompanying list of the other federal laws, besides the Civil Service Reform Act, from which Congress exempts itself: the Occupational Safety and Health Act, the Freedom of Information Act, the Civil Rights Act, the Equal Pay Act, the National Labor Relations Act, the Privacy Act, the Age Discrimination in Employment Act, plus the District of Columbia's health, fire safety and building construction codes.

Some of these exclusions are familiar. Taken together, they convey an impression of a towering citadel of privilege resting at a place where equality under the law ought to be the guiding rule. The rest of us should not have been sitting idly by, deferring, mostly by saying nothing, to this anomaly. The change that would allow the cafeteria workers to organize should be only the beginning of a long overdue process of review.