The Supreme Court on Monday cleared the way for President Trump to remove a Federal Trade Commission commissioner and agreed to resolve long-standing constitutional questions about White House authority over independent agencies. In an unsigned emergency order, the justices said they would permit the dismissal of Commissioner Rebecca Kelly Slaughter while the case proceeds. They also agreed to hear arguments in December, signaling that the Court is prepared to revisit—and possibly overturn—a 1935 ruling that limited presidential authority over the FTC and similar commissions. Trump had removed Ms. Slaughter, a Democratic commissioner, earlier this year, contending that the statutory protections...