in the belief that they had grants of authority

"In a phone call on January 30, 1981, Edwin Meese encouraged President Ronald Reagan to issue a pardon, and, after further encouragement from Felt's former colleagues, President Reagan pardoned Felt.

The pardon was signed on March 26, but was not announced to the public until April 15, 1981. (The delay was partly because Reagan was shot on March 30.) In the pardon, Reagan wrote:

During their long careers, Mark Felt and Edward Miller served the Federal Bureau of Investigation and our nation with great distinction. To punish them further — after 3 years of criminal prosecution proceedings — would not serve the ends of justice.
Their convictions in the U.S. District Court, on appeal at the time I signed the pardons, grew out of their good-faith belief that their actions were necessary to preserve the security interests of our country. The record demonstrates that they acted not with criminal intent, but in the belief that they had grants of authority reaching to the highest levels of government.

Nixon sent Felt and Miller bottles of champagne with the note "Justice ultimately prevails."