He was known as the Galveston Giant—a boxer who fought his way toward the first world heavyweight title held by an African-American. But in 1912, Jack Johnson became something else: a wanted man. Accused of violating the Mann Act, which forbade transporting a woman across state lines for “immoral purposes,” Mann’s relationships with white women got him in trouble with the law.

Now, 72 years after his death, President Trump has pardoned Johnson. The pardon took place during an Oval Office ceremony during which Trump referred to Johnson as enduring “what many view as a racially-motivated injustice.” President Obama’s administration had considered pardoning Johnson, too, but declined to do so due to allegations he physically abused women.

Johnson wasn’t the only person affected by the Mann Act. Also known as the White-Slave Traffic Act of 1910, the law was invoked over and over again to punish black men for their relationships with white women—affairs that challenged the racial status quo. Rooted in fears of women’s growing mobility and racist characterizations of the sexual appetites of non-white men, the law was designed to protect women against the supposed scourge of “white slavery,” a term used to refer to sex trafficking in the early 20th century.

Though it’s been significantly amended since 1910, the law, which was also used against figures like Chuck Berry, is still on the books.

As women gained more autonomy at the end of the 19th century, the concept of “white slavery” sparked a public panic. Reformers worried that women who appeared in public without men were being forced into prostitution by gangs who trafficked in young girls. This supposed sex trade was characterized as a “curse to humanity” in books like Fighting the Traffic in Young Girls: Or, War on the White Slave Trade. The popular tract warned parents about the supposed dangers of living or working in cities, taking public transportation alone, visiting ice cream parlors or restaurants, and congregating in dance halls, which one essayist called “truly the ante-room to hell itself.”

Johnson, then one of the most famous black men in the United States, was one of the law’s first victims. When he beat a white boxer, undefeated heavyweight champion James J. Jeffries, in a highly publicized bout in 1910, it triggered race riots. It also made law enforcement take a closer look at Johnson, who was known for his flamboyant behavior and lavish spending. This behavior had long rankled those who thought an African-American man should know his “place” and stay in it—and Johnson’s open relationships with white women were considered a slap in the face to racial norms.

Then, in 1912, prosecutors got their chance to enforce the Mann Act when Lucille Cameron’s mother accused Johnson of kidnapping her daughter and transporting her across state lines. Though Johnson was in a consensual relationship with Cameron and would soon marry her, prosecutors used the accusation as a pretext. As Chicago police arrested him for kidnapping, federal prosecutors assembled a grand jury to investigate his relationships with white women.

There was just one problem—Cameron, who was in love with Johnson, refused to say anything that incriminated him. Then, prosecutors found out Cameron had been a prostitute, which undermined her credibility as a witness. They dropped the case temporarily, but not before the public caught wind of it.

As historian Al-Tony Gilmore writes, the public felt that “the champion was such a bad character that it was their obligation to destroy him by any means available.” Prosecutors soon hit on another excuse to enforce the act: Johnson’s past relationship with Belle Schreiber, a white prostitute who agreed to testify against him. Schreiber’stestimony, along with Johnson’s recent marriage to Cameron, convinced the jury that he’d run afoul of the Mann Act and taken her across state lines for “immoral purposes.” An all-white jury convicted him and he was sentenced to a year and a day in prison.

Defiant, Johnson refused to serve his sentence. He went to Canada with Cameron, then fled to Europe and lived abroad for seven years. Gilmore notes that, as a result of the case’s notoriety, lawmakers introduced bills to ban marriage between black and white people in multiple states. Though none passed, the attempts illustrate how preoccupied the nation was with Johnson’s interracial relationship and his supposed “crime.”

Johnson spent some of his time in exile defending his heavyweight title but was defeated by white boxer Jess Willard in a bout in Cuba in 1915. Eventually, Johnson did return to the United States, and he was forced to serve his sentence in 1920. After his release from prison, he tried to revitalize his career but struggled to remain relevant.

Meanwhile, the Mann Act remained in effect. During the first half of the 20th century, the law was primarily used to prosecute men crossing state borders with underage women or during premarital or extramarital affairs. In 1944, for example, Charlie Chaplin was prosecuted—and eventually acquitted—for buying train fare for his girlfriend, Joan Berry, with the intent of transporting her across state lines within the context of a consensual relationship in 1941.

The law also remained a potent tool against black men whose relationships with white women infuriated white supremacists. In 1959, Chuck Berry was prosecuted under the Mann Act for employing—and allegedly instigating a sexual relationship with—a 14-year-old white girl, Janice Escalanti. A Mann Act accusation and three trials followed.

“He said he felt hounded by the police for his association with white women,” wrote Bernard Weinraub in the New York Times. “In the trials, which took place before white male juries, the prosecution depicted Mr. Berry as a sexual predator, and the outcomes seem, to some degree, racially motivated.”

However, the outcome of the trials also was predicated on Berry’s alleged involvement with a teenage girl—a relationship that haunted his later years. For years, Berry denied that he went to prison at all, but his fans and biographers couldn’t forget the allegation or the conviction.

These days, the Mann Act is still in force, though it’s been stripped of gender-specific language and updated to clarify that it’s only applicable to sexual activity that’s considered criminal. That put a stop to its use to punish extramarital affairs, “immoral” conduct like premarital sex, and interracial relationships. But though its meaning has changed, the legacy of the Mann Act persists.

Today, Johnson wouldn’t be prosecuted or convicted under the law for daring to have an open relationship with a white woman. But though he’s been pardoned, the effect of the trial and conviction on his life, career and legacy can’t be undone. Whether the law was applied fairly or not, prosecutors succeeded in punishing a prominent African-American man for his love life.