WASHINGTON — The Federal Election Commission will not adopt new rules governing the independent political groups that played a major role in the 2004 presidential campaign, freeing them to raise and spend unlimited sums of money during this year's midterm elections.

A federal judge had ordered the FEC either to write new rules or more fully explain its current policy for regulating 527 groups. The commission announced on May 31 that it would explain more fully the current policy, which is to deal with 527 groups on a case-by-case basis.

The groups, which are named after the section of the Internal Revenue Service code governing them, include America Coming Together and the Swift Boat Veterans for Truth. ACT spent millions criticizing President Bush during the 2004 race, while the Swift Boat Veterans spent millions challenging the Vietnam War military record of his Democratic opponent, Sen. John Kerry of Massachusetts.

Critics argue that the FEC's decision not to write new rules for 527 organizations has effectively left them unregulated. They note that many complaints against the organizations have been pending before the FEC for more than a year.

The FEC has countered that it would be unwise to issue a broad rule governing diverse groups.

U.S. District Judge Emmet G. Sullivan ruled in March that, "Judging from FECs track record in the 2004 election, case-by-case adjudication appears to have been a total failure."

However, Sullivan did not order new rules. The election commission announced that it would not appeal Sullivan's ruling.