An all-white jury convicted Johnson in 1913 under the Mann Act for taking his white girlfriend across state lines for "immoral" purposes.
He said Stallone called him to share Johnson's story, adding that the boxer's "trials and tribulations were great, his life complex and controversial". "Others have checked out this through the years, most thought it could be carried out, however sure, I'm contemplating a Full Pardon!"
He was convicted under the Mann Act, a law that was meant to prevent human trafficking and protect women against prostitution, but its critics say the law was used in racially motivated prosecutions of African-Americans and to punish political dissidents.
American heavyweight boxer Jack Johnson (1878-1946), is pictured along with his spouse on board a ship on this undated inventory picture. More recently, the documentary "Unforgivable Blackness: The Rise and Fall of Jack Johnson", directed by Ken Burns, was aired on PBS in 2004.
Johnson didn't serve his prison sentence until 1920 because he left the country following his conviction.
Advocates, including Sen. John McCain (R-Ariz.), have petitioned the Justice Department to move forward with a pardon for Johnson for years.
Mr McCain previously said Johnson was a "boxing legend and pioneer whose career and reputation were ruined by a racially charged conviction more than a century ago". He died in 1946.
In 2016, then-Sen. Harry Reid and Sen.
Activists and family members have long advocated for Johnson's posthumous pardon, as have US officials like Sen.
The Rocky actor has asked Donald Trump to pardon the late Jack Johnson, jailed for travelling over state lines with a white woman.
Posthumous pardons are rare... and Trump is a proven flake, so we won't hold our breath on this promise.
"While it is unfortunate that this unjust conviction was not corrected during the boxer's lifetime, a posthumous pardon today represents the opportunity to reaffirm Jack Johnson's substantial contributions to our society and right this historical wrong", the senators wrote in a letter to Obama.
In recent years, Sens. Cory Booker joined with McCain, King and Meeks to reintroduce a resolution urging Johnson's pardon. "I hope President Trump will seize the chance earlier than him to proper this historic flawed and restore a terrific athlete's legacy".