Once again, it comes down to John Roberts and Donald Trump. It was Chief Justice Roberts, of course, who wrote last year’s Supreme Court decision giving then-candidate Trump substantial immunity from criminal prosecution.

Chief Justice John Roberts' rebuke of President Donald Trump's call to impeach a judge marks a growing showdown between Trump and the courts.

Roberts, as the head of the federal judiciary, has been facing mounting pressure to protect the courts from political interference. With a lifetime appointment, it remains to be seen whether the 70-year-old Chief Justice will take further steps to defend judicial independence as Trump continues his broadsides against the judiciary.