Advisory committees play a crucial role in regulation by the Food and Drug Administration. Before making major decisions on such fundamental matters as new drug approvals, drug safety warnings, and drug testing standards, the FDA often convenes an expert committee to make recommendations.

The FDA follows that advice most of the time and even when it doesn’t, the public exchange between the committee and the FDA staff is illuminating and often affects thinking not only at the FDA but also throughout the medical establishment.

The FDA naturally recruits committee members from the best academics and practitioners working on drug testing, drug safety, and especially, the extraordinary challenges of developing entirely new drugs. No one should be surprised to learn that the FDA often calls on the same top-flight scholars who perform research and consulting for the industry.

Some time ago, the FDA worked out a nice way to handle this potential conflict of interest. If it really wants to use someone with industry connections on an advisory committee, it grants a special waiver, announces the nature of that person’s industry involvement, and then proceeds to tap this expertise in a remarkably open manner. All committee actions including voting are public.

Unfortunately, this reasonable and transparent system has aroused a raft of FDA critics who think the FDA sacrifices scientific and patient interests in favor of the interests of self-seeking scientists and their industry patrons. Congress is now considering legislation that would essentially eliminate from FDA advisory committees anyone with any sort of conflict.

The FDA, which can read congressional tea leaves as well as anyone, recently moved more than halfway toward this position. The new rules, scheduled to go into effect in a few months, would with rare exceptions eliminate anyone with a financial conflict amounting to more than $50,000, such as from consulting, research funding, family stock ownership, and so on. Members with interests adding up to less than $50,000 would be prohibited from voting. That would leave all decisions up to those with no recorded conflicts of interest whatsoever.

When the FDA tries to fix something that isn’t broken, it is asking for trouble, and that’s what’s going on here.

Consider the work of one of the FDA’s more vocal critics, the Health Research Group at Public Citizen, a Washington, D.C., research and advocacy organization originally founded and then set free by consumer crusader Ralph Nader. In 2006, Public Citizen went to the trouble of documenting what they and others, including editors of elite medical journals, thought was a severe conflict-of-interest problem. The Public Citizen researchers sifted through 221 advisory committee meetings over several years. Then they recalculated all the vote tallies after removing the votes of everyone with an industry conflict.

Let us give credit to Public Citizen, which proceeded to publish what must have been very surprising results in the Journal of the American Medical Association. Not one significant vote changed. No drug approval recommendations, no pronouncements on drug safety, and so on, would have been different if the “conflicted” advisory committee members had not been allowed to vote.

And that’s not all. The FDA pointed out that most advisory committee conflicts did not involve the manufacturer of the drug under review, but manufacturers of competing drugs. If we assume that a vote to approve a new drug is a vote against their own self-interest, these “conflicted” members actually tended slightly to vote against their own vested interests.

That may puzzle FDA critics who expected something alarming, but it shouldn’t. The influence of consulting, research funding, and the like, is far less potent than is widely assumed. A vote for a new drug does not necessarily endanger research funding from a competing firm; it may even do the opposite. And an apparently pure and unconflicted researcher actually may have a deep personal interest in seeing a new drug approved that vindicates a long line of his own independently funded research.

Fundamentally, the typical advisory committee member, whether “conflicted” or not, trades in the most important coinage of all, his own reputation among his peers. A vote that seems too close to financial rather than intellectual influences will arouse the kind of suspicion that in the long run is far more important than future consulting or speechmaking contracts.

Does that mean that the new FDA rules don’t matter? Not at all. The rules will tip advisory committees away from researchers deeply involved in drug development and toward the more ivory-tower types who are more comfortable with endless research than they are with forging the tough tradeoffs necessary to get potential therapies through the FDA’s arduous drug approval regime and to the bedsides where they are desperately needed.

Congress has pushed the FDA too far. The FDA should pull back from its ill-advised plan to reject much of the best available expert advice.

Mr. Calfee is a resident scholar at the American Enterprise Institute, which receives a small portion of its funding from pharmaceutical firms.