ASSIGNED BY Congress to write regulations implementing the McCain-Feingold campaign finance law, the Federal Election Commission has instead spent the past few years writing and defending rules that would undermine it. Last year a federal district judge rejected the regulations, using phrases such as "render the statute largely meaningless" and "create an immense loophole." Last month the federal appeals court here agreed. The commission is now said to be considering whether to ask the full appeals court for review or to try to take the case to the Supreme Court. Instead, it ought to stop fighting the law and start enforcing it.

The campaign finance law, also known as the Bipartisan Campaign Finance Reform Act (BCRA), sought to close the flow of "soft money" -- unlimited donations from corporations, labor unions and wealthy individuals -- to federal campaigns. In trying to make the shut-off effective, Congress also prohibited federal political candidates from raising soft money for state parties and outside groups; it said they couldn't "solicit" or "direct" such funds.

But in writing its regulations, the FEC interpreted "solicit" to mean explicitly "ask" -- rejecting proposals that soliciting include suggesting or recommending soft-money donations. But as the appeals court, in an opinion by Judge David S. Tatel, correctly found, the FEC's cramped definition would "reopen the very loophole" it was supposed to close. "Whereas BCRA aims to shut down the soft money system, the Commission's rules allow parties and politicians to perpetuate it, provided they avoid the most explicit forms of solicitation and direction," Judge Tatel wrote.

He said the agency had done much the same in its rules restricting candidates and political parties from coordinating their activities with outside groups. The point of these coordination rules is to prevent candidates and political parties from evading the limits on campaign contributions. But the FEC's rules essentially leave candidates and outsiders free to coordinate their activities as long as they do so more than 120 days before the election. If communications don't recycle official campaign materials or expressly call for the election or defeat of a particular candidate, according to the FEC, they won't be considered coordinated.

As Judge Tatel explained, this 120-day window -- an arbitrary period for which the FEC offered no justification -- "offers politicians and their supporters an unreasonably generous safe harbor." For example, he noted, "a candidate may sit down with a well-heeled supporter and say, 'Why don't you run some ads about my record on tax cuts?' The two may even sign a formal written agreement providing for such ads. Yet so long as the supporter neither recycles campaign materials nor employs the 'magic words' of express advocacy . . . the ads won't qualify as contributions" to the candidate. The FEC, he said, "has in effect allowed a coordinated communication free-for-all for much of each election cycle."

The FEC has the difficult task of trying to write rules that are clear enough that they don't impermissibly infringe on protected political speech. But as two courts have now found, the agency's desire for clarity can't trump its responsibility to follow the law as Congress wrote it.