JOHN YANG:

Last year, Arpaio was defeated in his bid for a sixth term as sheriff. The same night, Mr. Trump won the White House and the power to give Arpaio a presidential pardon.

We take a deeper look at this controversial pardon with Brian Kalt. He's a Michigan State University law professor and the author of "Constitutional Cliffhangers: A Legal Guide for Presidents and Their Enemies."

Mr. Kalt, thank you so much for joining us.

From your perspective as a constitutional scholar and professor of law, what make this pardon so noteworthy?