THE Trump administration recently announced that it intends to review, and presumably overturn, the Obama-era fiduciary duty rule that is scheduled to take effect in April. The administration’s case was articulated by Gary Cohn, the new director of the National Economic Council.

Mr. Cohn, most recently the president of Goldman Sachs, called it “a bad rule” and likened it to “putting only healthy food on the menu, because unhealthy food tastes good but you still shouldn’t eat it because you might die younger.” Comparing healthy and unhealthy food to healthy and unhealthy investments is an interesting analogy.

The now-endangered fiduciary rule is based on a simple — and seemingly unarguable — principle: that in giving advice to clients with retirement funds, stockbrokers, registered investment advisers and insurance agents must act in the best interests of their clients. Honestly, it seems counterproductive to go to war against such a fundamental principle. It simply doesn’t seem like a good business practice for Wall Street to tell its client-investors, “We put your interests second, after our firm’s, but it’s close.”

The annulment of the government’s fiduciary rule would clearly be a setback for investors trying to prepare for retirement. But the fiduciary principle itself will live on, and even spread.