Retired boxing champ Mike Tyson is spearheading a new campaign urging U.S. President Barack Obama to posthumously pardon African-American ring legend Jack Johnson, who was convicted for taking his white girlfriend across state lines 100 years ago.

The late sportsman was found guilty of violating the Mann Act in 1913 after taking his future wife Lucille Cameron across a U.S. state border for what the all-white jury deemed to be an immoral purpose.

He was sentenced to a year and a day behind bars for the offence, despite being in a consensual relationship with Cameron, but now activists are seeking to have Johnson's record officially wiped on the grounds of racial prejudice.

U.S. Senators Harry Reid and John MCCain have both taken up the cause, and Tyson is adding his voice to the campaign after meeting with Nevada representative Reid on Tuesday (02Apr13).

Tyson has now set up a petition on calling on fans to show their support for the issue.

In the call to arms, the fighter writes, "Let's show President Obama and the White House that we too care about Jack Johnson's legacy by signing this petition. In doing so, we are also righting the legacy of our great country."