Authorities begisn to think about  ways to bring him down through his relationship with white women.

  A new law is created, called the mann act, making it illegal to transport women across date lines for immoral purposes. It was also created in part to entrap Jeff Johnson. With the Mann Act in place, the cops got a lead about one of Johnson's girlfriends, named Lucio Cameron. The tip actually comes from Lucio's mother who doesn't want her daughter  dating a black man. 

  Cameron Lucio's mother goes to the police and tells them to arrest Jack Johnson for kidnapping her daughter. Lucio's mother tells the press  I would rather have my daughter locked up forever in an insane asylum than become the plaything to this  .

   Lucio thought another way. She actually loves Jack Johnson. She claimed she had already  been a prostitute so Jack Johnson didn't force her into that, and that they had a bonafide relationship. so the case falls apart.

  The bureau of Investigation tries to search out other leads for possible girlfriends to implicate Jack Johnson. They find a woman named Belshiriver who again was  another prostitute that Jack Johnson met in Chicago back in 1909 before the Mann Act was passed.

but that didn't seem to bother federal authorities.

  Because Belshiriver was a scorned ex-girlfriend, she decides to cooperate with the police and presses charges.