LAST YEAR PRESIDENT CARTER vetoed one of the most important legislative achievements of the 95th Congress on behalf of the District of Columbia. It was a bill to stop a taxpayer-supported gravy train that could ride the town to financial ruin: the police and firefighter disability-pension system, also known by Sen. Thomas F. Eagleton's description of it as "far and away the premier rip-off system in the United States." This legislation is set for a reprise, and its enactment is more important than ever.

Under the system that Congress itself created about 50 years ago, disability retirements are numerous and fat. At one point, for every regular retirement there were four disability retirements-and that's a lot of benefits, equalling 70 percent of current pay (tax-free) plus the same share of all future raises given to on-duty employees. Though the proportion of disability retirements has dipped in the last year, that's one gigantic tab for the city to pick up. The burden gets worse, too-for none of these liabilities has been truly financed. There's no fund to take care of these costs.

Last year's bill, the product of much hard legislative work by Sen. Eagleton and Rep. Ronald V. Dellums and their subcomittees, would have stabilized the shaky financing of pensions not just of police officers and firefighters, but of municipal judges, school administrators and teachers as well. The measure would have authorized the spending of up to $65 million a year in federal money for 25 years, and it would have tightened disability provisions for newly hired people (but not those already on the payroll).

Unfortunately, White House advisers misread the measure as just another big federal-spending bill and Mr. Carter let it die unsigned at Camp David in November. But now Chairman Dellums and Eagleton have reintroduced the Houes-Senate proposal of last year and have scheduled prompt hearings. Having thoroughly considered this measure before, Congress need waste no time sending it back to Mr. Carter. This time, the president should join Congress in recognizing the urgent necessity of a sound-and tighter-pension-fund system to replace the fiscally shaky and expensive system that continues to soak the city.