The right to freedom of speech allows Trump to make demands of the Fed to his heart's content. But legally, he cannot compel the central bank to lower its benchmark interest rate. The Fed has the right to act independently, and its aim is to promote a healthy and stable economy by keeping inflation in check.

The Supreme Court said in May that it could block any attempts by the White House to dismiss Powell, noting as part of a separate ruling that the Fed “is a uniquely structured, quasi-private entity.”...