President Donald Trump plans to use tariffs in the coming days to pursue a range of disparate and sometimes conflicting goals, from pressuring neighboring countries on immigration and boosting domestic manufacturing to penalizing trade partners for their own tariffs. 

Critics, including longtime free-market economists and trade experts, have criticized Trump’s tariff plans as incoherent and economically damaging. 

Payback and projection have long been two of President Trump’s touchstones. He settles scores in return for every perceived slight and accuses his targets of what he has done himself. In his second term, that approach has bled into the law, with perilous consequences.

More than most other areas of presidential authority, the Justice Department gives Mr. Trump a way to settle scores — and to help friends. Of course, no one can be convicted without a guilty verdict, but simply by launching an investigation, the federal government can impose ruinous reputational and financial costs.