OF THE THREE branches of government, the one that will have the most difficult time meeting Gramm-Rudman budget-cut targets is certainly the judiciary. Congress can cut large support staffs and reduce committee travel. The executive branch can eliminate whole programs and entire independent agencies. But the courts have no control over their workload and no abundance of superfluous job slots that can be reduced. Every judge in the federal system is needed, and each one has to have a courtroom, a few clerical assistants and facilities for keeping track of pleadings, trial transcripts, evidence and an occasional prisoner. There's not much fat to be pared or duplication of function to be avoided.

The Judicial Conference of the United States nevertheless gave it a try and came up with some proposals to present to Congress. A moratorium on buying new furniture, for example, will save $4.5 million between now and the end of the fiscal year. Limiting the use of express mail to real emergencies would produce a $50,000 saving. And making jurors pay for their own meals would leave $80,000 in the courts' coffers. The latter suggestion may be a reaction to a New York panel that astounded court officials by demanding such a quantity of gourmet fare during deliberations that it became known as "the jury that ate Brooklyn." We have our doubts about sending a baliff into a jury room to take lunch orders and face the accompanying hassles: "Who had the Diet Coke with caffeine and who had the regular Pepsi without?" The resulting delay, dispute and disruption will probably add to the cost of taking care of jurors.

There is a score of other detailed suggestions indicating that the judges have really taken a hard look at expenses. Closing two of the three public entrances at the U.S. Courthouse here, for example, would eliminate the need for seven security officers and save $41,000 by October. Holding circuit conferences only every other year would save $1 million in fiscal '87. The judges even suggest a few changes -- charging the Justice Department for the use of grand jury rooms, keeping filing fees now turned over to the Treasury -- that don't actually save money, but shift an expense to someone else's budget. Taken all together, you can see that these modest economies will not make a significant dent in the national debt.

There is, however, one single reform that would produce a saving of $200 million a year -- a fifth of the judiciary's entire annual budget. Diversity jurisdiction should be eliminated. There is no longer any reason for the federal courts to have to handle litigation simply because the parties come from two different states. The House has twice passed the requisite legislation. The Senate should act now, not simply because the reform would save money but because it makes sense.