THE GOOD NEWS is that the Federal Election Commission has won victories in two important cases. The bad news is -- well, you begin to get the idea when you know that the cases arose in the 1982 and 1984 campaigns. The FEC has done a good job of closing the barn door, but the barn has been empty for years. The question is now whether, in comparable future cases, the commission can get it closed in time.

The first of these victories came in a case brought against NCPAC concerning the 1982 senatorial campaign of Bruce Caputo. NCPAC (under the name of "New Yorkers Fed Up With Moynihan") made what it claimed were "independent expenditures" substantially above the amount it could contribute directly to Mr. Caputo's campaign. That's legal, so long as "independment" means what it says -- i.e., that there is no collusion or contact between the contributor and any candidate who is a beneficiary. But in this case both NCPAC and the Caputo campaign used the same pollster, Arthur Finkelstein. They could hardly be said to be independent unless the Caputo side of Mr. Finkelstein's brain refrained from communicating with the NCPAC side. The FEC sued NCPAC and won in federal court in Manhattan -- but not until last Friday.

The second case was brought against the National Congressional Club and Jefferson Marketing, both controlled by associates of Sen. Jesse Helms. The charge is that Jefferson Marketing provided services to Helms-backed candidates at rates so far below market rates that they amounted to contributions above the limits set by law. Jefferson Marketing has signed a consent decree, agreeing to separate its ownership from the Congressional Club and to pay a $10,000 fine. This may prevent future violations. But a $10,000 fine seems a small price to pay for a violation that may have affected the outcome of a Senate campaign in which $26 million was spent and which was decided by 86,000 votes of 2.2 million cast.

These cases may be moot for most of the parties concerned: Mr. Caputo, for one, withdrew from the 1982 race long before the election, when it was revealed that his claim to have served in the military was false; NCPAC has had its financial woes of late. But the principles remain important, and the results show that the commission can do something about those who wink at the law. The mystery is why these cases took so long.

For this some blame must go to the defendants, who predictably delayed things as much as they could, and some to the courts; the FEC went to court against NCPAC in February 1984 and against Jefferson Marketing in February 1985. But blame must also go to the commission. These violations were about as clear-cut as one can find, and the complaints were brought well before the elections. Yet the FEC took 20 months to find probable cause that NCPAC violated the law -- 14 months after the election. In the Jefferson Marketing case, the commission made its finding 17 months after the complaint and three weeks before the election; but it allowed another four months for "conciliation." The FEC needs to act more quickly. As things now stand, those who obey the law are not to be put at an unfair disadvantage by those who violate it.