Johnson violated the Mann Act in 1913 when he took a white woman across state lines to have consensual sex with her. The woman would eventually become Johnson's wife, reports the Associated Press.
"I've been a very big fight fan, I was a mediocre boxer myself," McCain told the AP. "I had admired Jack Johnson's prowess in the ring. And the more I found out about him, the more I thought a grave injustice was done."
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Similar legislation to pardon Johnson failed in 2004 and again in 2008 but McCain hopes that President Barack Obama will join him for the symbolic pardon.
"It would be indicative of the distance we've come, and also indicative of the distance we still have to go," said the former Republican presidential candidate.
Johnson fled the country after his conviction, but returned to the U.S to serve his 10-month jail sentence. In 1908, Johnson won the world title by beating Tommy Burns. He lost his title in 1915.
The Mann Act has been amended over the years, but not repealed. The act bans the transportation of woman over state lines for immoral purposes, according to USA Today.
Johnson died in 1946 at the age of 68 in a car crash.