The Post, after examining the health of our union's case against U.S. Customs Service drug testing {"Drug Tests: The Courts Say Yes," editorial, June 9}, has pronounced the patient dead. Therefore, the prognosis for its cousin, our suit challenging the president's drug-testing executive order, is equally bleak, The Post surmised. The remedy is to be found on Capitol Hill, where skilled congressional surgeons can cut and stitch, doing their best to lessen the pain of the drug-testing cancer, the editorial concluded.

Well, The Post is wrong in two of its three opinions on the fight against federal employee drug testing.

First, the Customs case is not dead. True, the Supreme Court has not looked favorably upon our requests so far, choosing neither to stay testing pending our appeal nor to expedite consideration of our case. But don't bury us while we're still breathing. The constitutionally protected right to privacy still hangs in the balance for thousands of Customs workers who now can be required to produce urine samples on demand while we await a reply from the high court.

Second, while the Customs and executive order cases are related, they are distant cousins. The Customs suit deals with one agency charged with drug interdiction and potentially several thousand employees; the executive order affects the entire civilian federal work force and more than 1 million workers. Though the appeals court said testing of Customs personnel is reasonable, to believe therfore that any court will agree to testing of half the government population is preposterous.

However, we join The Post in its call to Congress to right the wrongs that the courts overlook and strongly support the congressional actions taken against drug testing to date. The House already has passed a bill prohibiting the use of supplemental funds for drug testing under the executive order. And our union has been busy working with the congressional friends of federal employees, drafting legislation to choke off the constitutional abuses inherent in the drug testing order.

Our union's court battles over drug testing are far from over, but Congress cannot delay further action. Every unnecessary drug test is an affront to employee dignity. Every false positive test result can ruin a worker's future. Our people and Congress cannot afford to wait any longer. -- Robert M. Tobias The writer is president of the National Treasury Employees Union.