Presidential pardoning is one of the most powerful political tools available to a sitting U.S. president.
With the stroke of a pen, the commander in chief can forgive someone for their crime and restore the civil rights they lost. The move can go virtually unchallenged by other branches of government, and with that kind of sweeping power often comes questions and controversy.
Here's how presidential pardons work.
Presidential pardoning power was written into the Article II, Section 2, of the Constitution. It went into effect in 1789. It says the president "shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment."
So as long as it doesn't have to do with impeachment, most federal, but not state, crimes are fair game for pardoning.
There's no limit to how many people a president can pardon. Franklin D. Roosevelt holds the record with a whopping 2,819 during his time in office from 1933 to 1945.
The Constitution isn't exactly clear on how far presidential pardoning power can be extended. Now, President Donald Trump is testing the idea that he could pardon himself.
A court has never officially decided on the question. But a nonbinding 1974 memo suggests that while the president cannot pardon himself, there is a scenario in which the vice president could pardon the president.
Even though it would not be able to save Trump from an impeachment, it could still protect him from criminal, if not political, consequences.
— CNBC's Dan Mangan contributed to this report.