The problem with private pension plans used to be that they were underfunded. Then Congress, in one of the most successful reform acts in many years, restructured the pension world with the Employee Retirement Income Security Act of 1974, ERISA. Now, thanks in part to ERISA, in part to a turn in the economy, the opposite problem exists: some pension plans are overfunded. Companies want to take back the excess funds for other purposes; employees are resisting. The administration tried to broker the issue last year, but the rules it finally wrote are too weak.

The new dispute has to do with what almost everyone agrees is the strongest kind of pension plan. The employer does not just promise to make certain contributions to a trust fund each year, as in some cases. He promises to pay defined benefits. If the pension fund is not well invested or the stock market falls and it turns out the fund cannot support those benefits, the employer has to make up the difference. He bears the risk.

In the last several years, however, as inflation has come down, the risk has faded. Pensions tend to mirror wages, and wages mirror inflation. The lower the inflation rate, the lower a pension fund's likely future benefit costs. Lower inflation has also helped, this time around, to revive the stock market. The assets of pension funds have thus increased in value even as the funds' seeming obligations have declined. Large surpluses have developed.

The law says companies can get at such surpluses only when plans are terminated and all obligations to employees are paid off. The inventive response to this has been a wave of paper terminations. On Day One a plan is dissolved and some of its assets are used to buy annuities for all employees with claims against it. On Day Two a successor plan is created; some of the assets may also be used for this. The rest the company can pocket. UAL, Inc., parent company of United Airlines, announced on Monday it was reclaiming $962 million this way, the largest such reclamation so far. About 700 plans have been closed down since 1980 or are now in the process. The yield to employers will be about $6.6 billion.

Should employers be allowed to do this? They say yes because 1) the money is theirs, and their only obligation is to pay the promised benefits; 2) no company will run the risk of setting up this kind of pension plan in the future if it is not also allowed to enjoy the possible gain; and 3) a lingering pension surplus makes a company a tempting takeover target. You buy the company, terminate the pension plan and instantly recoup part of the purchase price. It happens.

The contrary arguments are that paper terminations make a mockery of the law; that employees also have some claim on the surpluses; that the rules put forth by the administration last year do not fully protect employees against loss of credit for years worked; and that companies are not fully taxed on the money they take out in terminations.

Difficult issues, even for specialists. But workers do need more protection than they have now, and both sides need more guidance. A few members of Congress -- Howard Metzenbaum in the Senate, Edward R. Roybal, chairman of the Select Committee on Aging in the House -- have been urging further legislation. They are right. Congress needs to step back in.