What is plenary authority, the phrase that caused Stephen Miller to freeze up during CNN interview?

What is plenary authority, the phrase that caused Stephen Miller to freeze up during CNN interview? - Miller suggests Trump ...
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'He Was Protecting Our Baby': Stephen Miller's Wife Katie Defends Him After He's Accused of Using Her as a 'Shield' During WHCD Incident

During an interview on The Ingraham Angle on Monday, April 27, podcaster Katie Miller defended her husband, White House Deputy Chief of Staff Stephen Miller, against viral claims that he used her as a ...