Mr. Cordray and the bureau have been doing what President Trump pledged to do in the campaign: protecting Americans from a system that has “robbed our working class.” So why would he want to fire Mr. Cordray? For one, Mr. Trump, despite his populist claims, has promised to dismantle the Dodd-Frank law, with the consumer bureau arguably the law’s most visible accomplishment. Second, the move may be part of a bigger power play.

Mr. Cordray is not the only agency head with statutory protections from removal at will by the president. The heads of the Office of Special Counsel, the Social Security Administration, the Federal Housing Finance Agency, the Federal Reserve, the Nuclear Regulatory Commission, the Consumer Product Safety Commission and other agencies are also shielded. Such protection is intended to insulate independent agencies from political interference.

But even if the full appeals court, which is hearing the case, rules that the president cannot fire Mr. Cordray at will, its decision could be appealed to the Supreme Court. The result could be a ruling that, if applied broadly, weakens the independence of agencies across the government.

The arguments against the bureau and Mr. Cordray are weak. But the political forces aligned against them are not.