SUPPOSE YOU retired at 65, began to collect your pension and Social Security and were having a fine time visiting your grandchildren, soaking up the Florida sun and improving your golf game. Then one day your old boss called and asked for your help. The office was shorthanded, a particularly difficult project had come up, and you were both knowledgeable and experienced. He couldn't offer you any pay, but wondered if you might come in out of a sense of loyalty, challenge or just because you had enjoyed your work. But suppose your boss added one final line: "Oh, by the way. Even though you won't be paid, if you take on this job you'll lose you Social Security benefit and you'll have to pay thousands of dollars in Social Security taxes on your pension." Still interested?

While such an offer might sound preposterous, it is exactly what has been proposed to hundreds of retired federal judges. The constitution requires that such jurists be given lifetime appointments, and it prohibits any reduction in their compensation. In order to allow older judges and those in poor health to retire, thus opening vacancies to be filled by younger judges, the law allows federal judges to assume "senior status" -- that is, to retire. Because of the constitutional mandate, their compensation remains the same, but because it is given for services performed in the past, not the present or the future, it has been treated as a pension rather than a salary.

There are now 760 active federal judges and 273 seniors. None of the latter is required to work, but because they are needed, almost all of them do, at least part of the year. Their contributions are important not only because they represent such a large proportion of the judiciary but because they are experienced. On Jan. 1, because Coness failed to extend or make permanent a special provision of the Social Security law, judges who continue to work as volunteers began to be treated as salaried persons rather than retirees. Their pensions are now treated as earned income, subject to Social Security tax and counted against the Social Securities earnings limitation.

Exemptions from the Social Security tax are, in general, a bad idea. But in this case, imposing the tax makes no sense. According to the Administrative Office of the U.S. Courts, federal judges are unique in that they continue to receive the same compensation before and after retirement. Imposing large money penalties on those judges who volunteer to work for no additional pay is pennywise and pound foolish. The present policy provides a substantial disincentive to judges who want to donate their time and talent. Congress, when it returns, should tackle the issue so that these critically needed volunteers will not be penalized for their public spirit.