James Allen: Must you go home?
Helen: There are no musts in my life. I'm free, white and 21.

—from “I Am a Fugitive from a Chain Gang” (1932).

The Worldwide Web isn't much help with the phrase. One assumes it was a semi-common, possibly regional (i.e., southern) comment back in the day, but I don't see any specific reference to it before this film—which, I should add, includes a lot of black actors in roles that, while mostly non-speaking, aren't too embarrassing for the time. The line subsequently wound up in a few other films from the era: “Dames” (1935) and “Kitty Foyle” (1940). It also became the title of indie movie from 1963 about an African American on trial for the rape of a white woman.